The only thing I really dislike about general D&D culture is the deep, abiding assumption by players and DMs that they're doing it wrong if things happen that the DM doesn't have a plan for.
I tend to think something is going wrong if my party always acts in ways that I have predicted--or rather if I have everything planned out ahead of time. But then again, I love to improvise--it's probably my favorite part of DMing--and it is the style that is least hampered by creative players.
Now it feels like as time goes on, D&D becomes more self referential. D&D isn't focused on being the best RPG for playing in a fantasy world that it can be. It seems to be focused on being the best RPG for playing in a D&D world that it can be. It feels like D&D stopped being influenced by popular fantasy and just started being influenced by itself. I mean sometimes D&D takes risks and comes up with some awesome new stuff that breaks new ground, but a lot of times it feels like it's primarily focused on updating everything that has been in D&D previously. It feels hypocritical at times because I really want to see an update for my favorite stuff from previous editions, but at the same time way back when it felt like any given new release was exciting because it might release something new that we have never seen before. Now there is this expectation that the next X amount of releases are going to retread old ground before they might even begin to do something really new.
I take the opposite preference on this, and think D&D
is at its best when it is trying to be the best D&D than when it is trying to do something new. However, I can sympathize with that not necessarily having been my view back in the TSR days.
So what has changed?
I think it really comes down to backwards compatibility. AD&D (1e+2e) lasted for a looong time, as editions go. They built up this multiverse with a lot of settings and ways they were connected. For a lot of us, that became D&D for us. New settings came out, and you could, if you so chose, get on a spelljamming ship, or hop through a portal and
go there. It was all a part of D&DLand.
So now we have a situation where D&D = D&DLand for a lot of people. Then they release a new set of rules, and for the majority of players, those rules are...better. I just can't play AD&D anymore--I got sick of the rules before the edition was even over (I actually stopped playing it in the 90s because the rules bothered me). So new rules are coming out, and I think, "Yay, now I can travel back to D&DLand!"
Except, I can't. Not without a bit of effort at least. The great wheel was more or less intact, except they gutted out some of the fun stuff. Half the compaign settings got, at best, authorized fan support, and the monsters you wanted right now were sprinkled over years and years of products, with initial releases filling up that space with the 'new and exciting.' New and exciting was great in 2e, because everything was going to be new and exciting, since publication continuity was still linear and unbroken. Once 3e came around my thought was, "Dangit--forget this new crap
until you have updated D&DLand to this new rules set!"
So it's not that the new stuff isn't interesting, it's that we never asked for the old stuff to be thrown out when the mechanics updated. I want D&DLand, and I don't want to have to spend massive amounts of time doing it myself (monsters are probably one of the most needed official updates),
so I can keep playing the same game I was with newer and better mechanics.
It's kind of like WotC is saying, "Okay, finish up your old campaign. D&DLand is no more. Try this sequel now!" What?! I didn't want a new game. It's New World of Darkness replacing Old World of Darkness--that isn't an edition change, that's a new related game. (4e, of course, was even worse than 3e in that regards).
5e is definitely a step in the right direction. They've recognized my demographic exists and realized that embracing D&DLand, along with the things that later editions added to it is better than just making a new related game world. There are still some issues with unfortunate and unneccessary continuity (I'm looking at you, Yugoloth backstory fiasco.) But in general, I don't have to do much to run D&DLand in 5e. All I really need now (other than psionics and some gestalt multiclassing rules) is another monster manual that includes many of the essential planar monsters to fill out the Great Wheel, and some other iconics (like gem dragons and more fey), and some basic spelljamming stuff, and I'm good to go with D&DLand in my favorite ruleset (5e). Then feel free to add all the worlds and settings you want. I can hop a ship and
go there.