I've seen multiple people adapt Dragon Age to 5e, including reworking every class to fit into the "mages are rare" nature of the setting. Then I turned my head to the left and looked at the Dragon Age RPG on my shelf.
That sounds a bit funny since Dragon Age was Bioware's spiritual successor to Baldur's Gate, which was just AD&D/2e adapted digitally. Going from D&D to Bioware's homebrew system and then back to a newer D&D seems like a lot of steps.
Oh, and you can see the steps. Bioware condensed the mental stats into cunning, giving them space to add magic and willpower. Then the RPG needed to add two new stats just to keep cunning from being too bloated.
Then they made Fantasy Age, which is the Dragon Age RPG without Dragon Age, and they immediately got rid of the magic stat.
Assembling the right mix of mechanics to perfectly match your setting/character concept is a whole game in itself. Sometimes I'll just build a character for the fun of it.
If it's written around epic heroism, why do we have levels 1-5? I don't think that's 5e's genre. It's also not low fantasy either, since even at low level you can't easily get rid of the magic-powered class abilities without a ton of homebrew.
In other words, I don't think 5e would run well in Dark Sun.
I can't speak to how well 5e would work with dark sun, but 5e is very much about epic heroism. Levels 1-3 exist entirely as an introductory system to avoid overwhelming new players - IIRC, there are official suggestions to just skip them if playing with experienced players. Additionally, they are designed to go incredibly fast. The meat of the game really starts after that, and the characters quickly catapult to functional super heroes.
Edit: any system that's described as "a pitch-black, apocalyptic TTRPG" and uses "scum" in place of "player characters" is ok by me.
FFS, the official tagline is "a doom metal album of a game. A spiked flail to the face. Light on rules, heavy on everything else;" what more do you fellow grimdank dorks want?
Changeling: the Dreaming fan here. Our system is better suited to the roleplay side of things, several sessions can go by without a single combat, and it's not the core focus of the system.
I love my WFRP campaign. I'm playing a noble's servant who got sent on a dangerous quest by his lord to "man him up a little," and he wound up getting mixed up with a party is complete nutcase. The rules have an odd kind of crunch to them - there's tons of details for combat, but my GM says there's basically no encounter design guidelines, for example. Still, it's a great time and I can't recommend it enough.
If I turn out to have more time at my new job, I plan to start thrid campaign (alongside 5e and Blades in the Dark campaigns I'm running now), and make it WFRP for two people who ran it to me + maybe one other person