The answer as GP points out is that in the majority of these cases open source software is still funded by capitalists. Wikipedia content presumably being largely a volunteer effort doesn't change this. Something still has to fund Wikipedia's existence. Wikipedia and signal for example are funded by nonprofits. I quite like this model which is why I suggested it in my previous comment.
The main point is that you can’t just tell everyone to work for free and still call it capitalism or even expect it to work at all. That’s what it sounds like you’re suggesting… I like your challenge to the capitalism/socialism dichotomy. I think your solution is lacking some sophistication in understanding how the open source landscape works, what motivates people and how to yield production, and is kinda out of touch with reality.