The problem is that Unreal exists and that's so far ahead it's hard to imagine how the OSS world can catch up. Glad to see that Godot is already thinking about streaming assets.
The licensing model of Unreal for small businesses is pretty attractive as well as they don't charge until you made 1M. If I made 1M with my game I certainly wouldn't mind paying 50k to Unreal on my next million.
On the other side, if I'm doing something for fun (read hacking on unfinished code) and I want to have the perfect abstractions, Unity and Godot are certainly not what I envision. I'd probably just work on something like Bevy.