from my experience, there will be a LOT more ne'er do wells being filtered than good users. Not because there aren't a lot of good users, but simply because there are a lot more low effort ne'er do wells attracted to internet forums.
Other users can still browse at the very least. I think this will capture that nice medium of "good user who doesn't mind a little incentive". Because ofc the highest quality users aren't posting their ideas on public forums at all
I don't think that's true. I published some of my privat projects only on reddit because I want to put them out there, but do not expect people to interact too much.
Not saying your project isn't high quality, but generally the most consistent stream of high quality projects has someone paying for them.
No, for privat projects I am mostly reinventing wheels. But, in some sense, I actually pitched them collectively during my job hunt.
My interests are spread pretty far, so my hobby projects range from building ambisonic microphones over reimplementing interesting algorithms like WFC to implementing Navient Stokes equations in JAX to optimize airfoils in a differentiable CFD simulator.
My new job reflects that, I am pretty happy with that :-)