I see this point a lot and I don't get it at all. You can do something awesome, free and open-source but use tools that aren't, especially when we're talking about community building. Sure, you can do your outreach exclusively on Mastodon or Farcaster, but the most eyes just happen to be on closed platforms, so it'd just be self-sabotage. Doing the only thing that makes sense doesn't make you a hypocrite.