I already replied to this kind of logic elsewhere (
https://news.ycombinator.com/item?id=30793257), but I don't see the logic of looking at Mozilla cutting support for a program then introducing a way to fund that program, and responding to that by saying, "why should I fund something that's seeing cuts?"
Hopefully it goes to MDN. Nothing about the scenario you describe would be improved by funneling money from MDN to Firefox, that would make the problem worse. What I'd like is for Mozilla to introduce ways to fund Firefox directly, not for the money to come from a different critical web resource.