To clarify: I'm not in favour of malthusian solutions.
It's true that the true problem is capitalism but let's not pretend like infinite population growth is good either. Yes, we can fix world hunger even with 10 billion but what if we grow past that? And we need to take into account that even if we can feed ourselves, is there enough for other species? I don't think that overpopulation is something we necessarily need to solve but I do think we need to stop thinking about population growth as something necessary, especially because in capitalism population growth is tied by the ruling class to economic growth.