I think we misunderstand each other at a fundamental level.
(I'm not saying you are in favour of PF1, its my system of choice.)
I'm not suggesting we support Wizards,
Any version of "keep playing 5E" supports Wizards. Yes, even non-Wizards 5E clones. Because, importantly, Wizards also produces content for 5E. So if you play Black Flag, a 5E variant, someone is going to eventually want to play an artificer or a species not covered by Black Flag and the artificer is right there in D&D...the other races are right there in D&D. So people will still buy Wizards books because they will still be compatible with Black Flag. Or A5E, or C7d20, or...or...or.
I'm not wanting to solve the problem of 5e being too dominant.
If you care about the hobby you should.
The point of the thread and the open question(s) are I guess
1. Can it even be solved.
Yes, easily. Stop playing and supporting 5E.
2. If not, how can it (5e dominance) be leveraged for good?
It can't. All 5E roads lead to WotC. That was literally the point of the OGL and now the CC-BY release of the 5.1 SRD. Supporting any of them will either directly or indirectly support WotC.
If your answer to the premise of the thread
The premise of the thread is: What's good for D&D is good for the RPG hobby. I fundamentally disagree with that premise. Quite the opposite. What's good for D&D is actively harmful to the RPG hobby.
'D&D is out there, and folk D&D is the answer' in the form of whatever version you like, thats a perfectly valid answer.
D&D is out there...and so are thousands and thousands of other games. Go play some. That's my answer.
Does it look like DCC? Maybe? I love the flavour of the free rules.
Sometimes, yes. Sometimes, no. DCC rocks. You should try it. But it's not just about D&D-adjacent games. It's about the industry as a whole. Traveller, Paranoia, Call of Cthulhu, Bushido, Fabula Ultima, Fate, Apocalypse World, Masks, Cartel, L5R, Mouse Guard, Mutant Year Zero, Wushu, Risus, Index Card RPG, Night's Black Agents, Outbreak, Cortex Prime, Cypher, WFRP, Broken Compass, on and on and on. Those games and so many more barely exist because D&D has a stranglehold on the industry. I'd love to be able to play all of them and more. I've offered to run most of those on that list. There just aren't players...because D&D has a stranglehold on the industry.
The issue is one of 3PP keeping the lights on, as you noted, and how that is done, within the realm of 5e being the overwhelmingly dominant space.
Right. And that very dominance is the problem