I've been funding it (a small amount monthly) for a long time now. I wish it had existed about 15 years ago in college when I had lots of time on my hands for toying with game making.
I'd fund it if I could use it to actually ship something and make money. I've donated to other software projects. If, say, for several thousand bucks they'd actually give me a tiny bit of support by fixing bugs in the "stable" branch that affect me then I'd pay up. At this point though if I want to actually ship using open source I find I can actually get things done faster using SDL2. Because SDL2 is a minimal layer over native if there is an issue I can actually figure out what native calls are happening in what order. If controller inputs are wonky or textures are the wrong color I can figure out why. Godot does try to use an understandability friendly subset of C++ (no template metaprogramming and such) but it is still too sophisticated for me to quickly dive in and understand how it all works; and it is certainly too complicated for its core maintainers to be able to quickly dive in and fix longstanding open issues in "stable".