You're not wrong that creating FOSS technologies is a worthwhile pursuit. I think what you're missing is how massive a game engine is. The average game development company simply cannot be creating its own engine or forking Godot to create a game in.

It requires a large company dedicated to engine development and tooling, and at least a decade of development, to create a worthwhile engine. If you want to make a game, fronting that development with a decade of engine development is not financially sensible. This issue is not one that game development companies can fix.

That said, if Godot meets your game and team's needs (or reasonably close to where you can reasonably develop the engine further to meet them), go for it. But it's not realistic for most developers.