Is Ravenloft the Best official D&D5 Setting?

Yes it is. No doubt

Oh reasons....sure
Actually its like my Planet Psychon in some ways...

1 Ravenloft is Mostly One Way Entry
Domains connect to other domains. You can come from any setting to Ravenloft. Once in Ravenloft, getting out is harder. You dont need to worry about the rest of the multiverse much.

2 In Ravenloft everybody is damned
All those normal villagers in the land. They are all damned too. If they die here and dont get their souls eaten or turn into undead, they get reincarnated in another domain. There is no escape for most people. The land may snatch you back if you escape. If your a horrible person like a murder hobo adventurer its no wonder you're here now. If you were good, maybe some power is testing you or wants you to beat a domain lord.

3 Ravenloft is a Prison
The domain lords are prisoners to whos tragic circumstances are used to make them suffer. Adventurers may be brought in as a test or challenge or to frustrate the domain lords. The truly good may be brought here to frustrate to prisoners and to test their zeal with corrupting dark power. Some good might be sent by a good god to help free commoners from suffering. Maybe adventurers give false hope to locals to crush their spirits. You might be here to be corrupted or to make sport for a domain lord or perhaps to make a villain of the realm suffer.

4 You Will Never Escape!
The world seeks to make you its creature and may offer dark gifts to help bind you to the nightmare realm. Maybe the dark forces tease you with escape then brings you back just to show your never free. The uk 60s spyfi show "The Prisoner" is a good show with this struggle. You might come up with stories of escape that lead you to some disaster. Maybe if a pair of mist traveller holds hands with others in between they could all travel. Maybe The Dark Powers let you loose for a bit and trick you back. Perhaps a hunchbacked angel or a hermit might know some secret out but the information is flawed or has unforseen catches.

5 Dark Gifts are Shackles
I quite like various versions of dark gifts. A new version is out but I dont really know if very different. Im making a rare change to these rules for my own game. I presented choices of dark gifts as boblets of fuid or a black dragon would eat them. The dragon gets kickbacks for encouraging others to take dark gifts but has to let you live. So in the older Ravenloft 5th ed book I found the gifts not good value as feats. But as bonus setting abilities, they are fine.

I have rewritten 4 ive offered so far in game. Im keeping the core benefits of powers and diluting the weakness. I'm redefining the bad stuff as Quirks, which might just be cosmetic. The 1in20 roll activates problems, the mechanic isn't too awful as you only get this effect once per long rest. I'm using all the fluff tables and disadvantages for cosmetic drama fodder not just mechanical effects. I will be fine if some creepy features come up in some situation and they are great roleplaying fodder not mechanical and too punitive as in the official versions.

To me dark gifts are signs of corruption you willingly accept that help bing you to the realm. I might offer them more in-game but escape from the realm depends on purging them. Some expert or location will reveal the means. My take on them is to make characters bound to Ravenloft and introduce personal spooky fluff drama for a more psychological character development. The tables and penalties described in the text are now just for ideas. Id rather have more narrative cosmetic effects than mechanical nerfs. I think a 1in20 chance of activating a weird effect is more just a reminder to have a side effect used in play. It is fine like this, but it feels more punitive by book. A few new book reviewers are complaining about these like they are new. Im probably waiting till the book goes on sale. 

Living Shadow
Grasping Shadow. You learn the Mage Hand cantrip if you don't already know it, and require no components to cast it. The hand created by the spell is shadowy but is not bound to your actual shadow. Your spellcasting ability for this spell is Intelligence, Wisdom, or Charisma (your choice when you gain this Dark Gift).

Shadow Strike. When you make a melee attack roll, you can increase your reach for that attack by 10 feet. Your shadow stretches and delivers the attack as if it were you. You can use this feature a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.

Quirk: Your shadow does odd things and looks strange sometimes. They might activate on a roll of 1 in play once between long rests or other times

Mist Walker
Misty Step. You can cast the Misty Step spell, requiring no spell slot, and you must finish a long rest before you can cast it this way again. Your spellcasting ability for this spell is Intelligence, Wisdom, or Charisma (your choice when you gain this Dark Gift). If you have spell slots of 2nd level or higher, you can cast this spell with them.

Mist Traveller. When you enter the Mists, intent on reaching a specific domain, you are treated as if you possess a Mist talisman keyed to that domain. To use this trait, you must know the name of the domain you have chosen as your destination, but you don't need to have previously visited that land. This trait doesn't allow you to bypass domain borders closed by a Darklord's will.

Quirk. You feel more comfortable travelling than staying in one place. Its as if the land puts roots in you and drains your dreams. You recover fatigue half speed, if you remain a week or more in the same bed or comunity. Prison would be awful.

Borrowed Eye (in players case watched by ancestral spirits)
As an action, you can influence the presence guiding the watchers for 1 hour. For the duration, you gain advantage on Intelligence (Investigation) and Wisdom (Perception) checks, and you can't be blinded. Once you use this feature, you can't use it again until you finish a long rest.

Quirk. Spirits are attracted to you and gossip about you, divination attempts vs you have advantage or greater effect. Spirits might become visible on a roll of 1 in play once between long rests or other times

Soul Echoes (visions of past life or incarnation from spirits)
Channelled Prowess. You gain proficiency in two skills of your choice.
Inherent Tongue. You can speak, read, and write one additional language of your choice.
Quirk. You get flashbacks and echoes from the past from spirits on a roll of 1 in play once between long rests or other times.

6 A Domain of Your Own
You can make your own bampagn for one or two sessions or longer. You can try other domains and ditch them quick. There are tons old splatbooks from the past to get ideas from. Lots of old ones on Drivethrough POD. You dont need a huge campaign setting, and you can bring up any environment you please. Make a setting you like. A mini domain to sample any idea without going whole hog. Made a dud? Let it break up, and the dark powers recycle it. 

7 Variety
Horror sub-genres and various pseudo-historical inspired fantasy let you try a huge amount of campaign styles.  Also, a variety of social encounters and ultra violence can be found with villages, ruins and haunted places. All kinds of scenarios can be amped up to be horror domains.

8 Villains
They are jerks you can unrepentantly kill if you can. Recycle old, dead campagn villains. Maybe they still return if the dark powers support them. But don't overdo this. Maybe a shadow of them is just felt in paintings and clues of some new domain lord's realm. Maybe these could be a bridge for the lord to return. A minor haunting might be a fragment of the old domain lord grasping at existence.

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Finally, I think the new thing most in line I'm waiting for is a book with all the core wizards in one book with new spells. They really need a deity book with gods and domain clerics. Wizards and Priests have a huge effect on world-building and are essential for the campaign, and not just for character use.

I hope we dont get these subclasses in dribs and drabs and do get something like the 2nd ed brown books for major classes rather than leave as an implied big project that never finishes. Maybe could do cleric and paladin book, ranger and druid book, rogue and bard book. Making an edition with no effort to complete basic game features seems a bit broken. I think they prefer small doses so they can sell books to players with player options to sell books.

Imagine one book of d&d5 with content only up to 10th lv and basic content to start play from dmg and mm. Then you could worry about high-level later and not let it take up your headspace beyond that. Obviously, a later book with 11-20 would be a less-needed option for most players. 

Partly, I play by core books and limiting non core book content on request. Ravenloft and Theros campagns help me narrow lots of game content. I do like one bastion feature in the FR players book for theros letting you have a druidic woodland weird sylvan peoples are attracted to. Honestly Id like a Bastion book with mundane building cost and times and some domain tables to run yearly play turns where you spend a season at home. Im exited by prospects of getting haunted Bastions.