D&D isn't one game anymore.
It is a mutant mix of everything.
You get groups that will base their play on a stable version of the game, most likely 2014, and they will take the best from everything else, including 2024, ToV, A5E, and various third-party books.
Since 2024 has not set the world on fire, the community collectively shrugged its shoulders, took the 2024 books, and used them as "patch notes" for their 2014 games. Sure, they may pick up a book, but so many are deeply bought into 2014 that they will not leave unless a new edition with a radical design shift comes along and changes everything.
You can do most of 2024, the best changes, while staying in 2014 with a page of errata. 2014 is arguably better and closer to classic D&D, with alignment, humanoid monsters, and races still in the older game. The whole background, ancestry, species, etc., character creation complicates character creation. It isn't D&D. I don't mind in other games, but we don't need this many "false choices" in D&D when the "do whatever you want" system in Tasha's was much better for classic D&D, or sticking with the racial ability score bonuses.
Only a dozen or so spells are broken. A few multiclass combos are broken, and this can be fixed with the limitations on action surge and the "one leveled spell" per turn limit. Most issues are fixed by limiting multiclassing to a roleplaying context instead of letting people build characters like an ARPG.
With a page of fixes, 2014 is the superior game.
Even Roll20's D&D with extra DM Guild content vastly differs from 2014 or 2024. The game is bizarre, built out of a Frankenstein patchwork of books and Roll20 supplements. While it is based on D&D 2014, the game is more like this strange, generic 5E unique to Roll20.
Roll20 D&D is nothing like D&D Beyond D&D once you fully kit the game. It is a freakish game, with almost a random assortment of spells, races, and subclass choices.
Add a page of community-sourced house rules to the game, and you have something superior to D&D 2024. These house rules can pull in the best D&D 2024 patches, but ignore all the problematic changes. Monks from 2024 and rangers from ToV are in the same party. Modded 2014 D&D with house rules is a better game.
Orcs and humanoids are still monsters, alignment is still here, half-orcs and half-elves have not been erased, and the game feels classic, yet wholly random and freakish.
It is Freak & D.
It is even different from A5E, which feels more like B/X D&D than mutant Roll20 D&D. Some of the best rules from this version are must-haves for F&D, and there is a lot from this game that will get pulled in, such as counter spell rules, exploration challenges, and much more.
ToV also feels vastly different, like another version of the basic game, like the D&D Rules Compendium. We have excellent class designs here; you are free to use them. I saw a game with the ToV ranger, the 2024 monk, and a few other classes from other books and publishers in one party.
However, the D&D game inside Roll20, fully modded with third-party content, is one of the closest things you can get to experiencing a version of F&D you can look at and play in the wild. Without VTTs, people have stopped caring and are mixing every game with every game and calling it 5E.
D&D feels like it died, and we are left picking through the game's ruins and modding it to be whatever we like. 2024 isn't a new version; it is the patch notes that people choose the best parts from and mostly ignore. D&D is a boneyard system these days, where we pick and choose parts to cobble together a game. This is the OGL fallout. Wizards lost that fight.
I wonder if D&D even has one set of defined rules anymore.
Everything is this generic "5E roleplaying," and the base version of that is "whatever 5E rulebook you happen to own." SRD included.
Even the base version does not matter anymore. What is your base game? 2014? ToV? A5E? 2024? The 5.1 SRD? Do you stick to one VTT's character designer, and that is your game?
That is the exception if you are a purist and want to play in one system, like a ToV or A5E table. It is nice since you have one "source of truth." I like the fixes that both the ToV and A5E teams made. I can play Roll20 D&D, which is a different version of 2014. I wish Roll20 supported both A5E and ToV (I know about the ToV announcement and it sucks).