Blender gets 135.000$/month through donations & sponsors
Godot hires 4 full time employees through donations
Krita got 4.200$ donation for this month (not sure about the other months)
Ardour seems to have 11.500$/month
etc.
I agree it is hard to reach a stable income through donations & sponsors but some open source project managed to do so, and I hope other will in the future.
There still room for many "Blender of XXX" (in the sense of a flagship FLOSS that is competitive with proprietary solutions).
I'd say Godot is well on the path of being the "Blender of Game Engines".
But there is still room for the Blender of Photo editing (Gimp is far behind Photoshop), the Blender of Vector/UX (inkscape is not on part with Figma/Illustrator), the Blender of Music (Ardour is nice but UX wise not as "modern" as Ableton or Bitwig), etc.
For someone who has some time + a strong commitment to pretty UX & clean architecture, I think there might be still my opportunities for donations & sponsors driven projects