Ha, there actually are engines, that many of the new RPGs share. But I am not sure D&D (or at least 5e) is well suited for being a base for many different games, because i.m.o. it has a strong focus on combat.
If you want a game with lot of encounters with monsters to defeat, getting more and more powerful to defeat even harder enemies, with combat system that is not overly complex but still tactical, you definitely could (and maybe even should) base your game on D&D
Heroic fantasy works. I could imagine Witcher, or Monster Hunter, even aliens style sci-fi reskin, fighting monsters in derelict space-ships should work... but i.e. Shadow of the Colossus would be harder, and Game of Thrones style political intrigue might turn into really simplistic dice-rolls.
But this is probably true of many games, i.e. I heard that Fate is really good if you want to do something with a structure of action-adventure tv-show, but probably not a psychological horror :P But doing i.e. politics in that system might be more fun than in i.e. base 5e D&D.
Probably the most succesful engine I have seen is in the powered-by-the-apocalypse games. Apocalypse World invented a really simple base machanic, where if your character wants to accomplish something, you roll two 6-sided die, sum the numbers, and if it is 10/11/12, you just do the thing, if it is 7/8/9, you do the thing, but something bad happens, and if it is 1 to 6, you don't do the thing and something bad happens.
Probably my favourite system I have played so far :-)
> you roll two 6-sided die, sum the numbers, and if it is 10/11/12, you just do the thing, if it is 7/8/9, you do the thing, but something bad happens, and if it is 1 to 6, you don't do the thing and something bad happens
Seems too similar to my real life experience. That's uncanny.
The powered-by-the-apocalypse engine sounds fantastic. Indeed as I read your comment I was thinking that one might want to repurpose the D&D combat engine to something more psychological, but the direction of the Apocalypse World engine sounds more interesting (and maybe profound) than anything I was expecting.
Dungeon World [0] is a hack/slash dungeon delving fantasy game using the AW engine. Fantasy isn't my bag, so I haven't played it. But it gets good reports. It won Indie RPG of the year, too.
It's fascinating that the thing you note about PbtA is its dice resolution mechanic. It wouldn't occur to me to focus on that.
The thing about it I think is so strong is its 'move' mechanic: the way it neatly and obviously separates role playing from game action, and helps players immediately feel like they're playing in the setting. It onboards newbies really well, and sets the scene without relying on the need to read a short story.
I'm not trying to say I'm-right-you're-wrong, it's just fascinating how things resonate with different players. I guess Vincent Baker's genius runs deeper than I thought!
There are other "d20 system" games - e.g. I remember the Babylon 5 RPG uses it.
I've reached the conclusion it's a bad idea though. The more generic a system it is, the less appropriate to the specific game it can be, and vice versa. So I much prefer systems that are very dedicated to their particular game experience. E.g. I absolutely love The Mountain Witch, which is a game that feels like a samurai movie, and everything in the system supports that: there's a special mechanic for duels, another for betrayals, all conflicts interact with your personal history/issues...
