That's a False Dichotomy. The option are not so close to 5e that it's not different enough and so radically different that it's another 4e. There are options in the middle where we still play the D&D that we know and love, but different enough from 5e that they could make a new OGL
They said that BEFORE their plans fell through on OGL 1.0a. Plans can and often do change when things like that occur.
A lot of those D&D beyond accounts have them because places like Foundry that do VTT better use D&D beyond content.
They have just given themselves an extra incentive to stick with 5e, not to move far enough away to make a competitor, using the very popular 5e rules, competitive. Why would they cede 5e?
Yeah - their plans falling through made keeping 5e as the chassis more vital than ever. So they don't create their own competition.
I'm profoundly doubtful that the tiny foundry user base contributes any meaningful users to DDB, but feel free to show me evidence to the contrary.
You haven't responded to my key ask: explain how they can change enough to lose backwards compatibility and make that work with DDB. That is the main question, and I suggest that if you (or anyone else) can't answer it, then you don't have an argument.
Edit: I suspect most of the "no backwards compatibility" arguments are coming from folks who don't use DDB. If you rely on it, the way millions of players do, and the way WotC clearly wants the game to go, then backwards compatibility seems like an obvious necessity.
I currently have dozens of books and a bunch of campaigns, encounters, home brew spells and items, characters, etc., all interlinked. Do you honestly think WotC is going to release a new PHB that doesn't work with all of that, on their coveted digital platform that they just spent $146 million on? What would I do with that PHB?
That's why a lot of these threads are nonsensical. WotC aren't going to remove a class or make fundamental changes to game mechanics, because they can't. They would break their own game. 5e is locked in. If you really want to understand this issue, you have to make an account on DDB and run a campaign through it. Just to understand the facts of what WotC is working with.
This is fundamentally different than previous edition changes. There is a new paradigm.