Would one solution to the free speech problem in social media is if we had state sponsored social media? The Government wouldn’t have a financial incentive to go after advertisers, and 1st amendment would actually apply.
Some things have an objective ick. Whether it's women not wanting to touch icky men or advertisers not wanting to have their ads next to their abstruse rants entailing sexism, racism, or fascism. The question is do you value your ick more than you value being prosperous or laid? A smart lawyer once said "You exist in the context of all in which you live and what came before you."
(I am personally sus that there are a lot of people who would actually use such a thing, but people seem to talk about it a lot)
But you say those sites have no reach. They have no reach because they're full of trolls. That's what would happen to any network no matter who owns it that attracts that kind of audience.
But most people aren't on mastodon, because most people don't care about a platform "resistant to the ideological whims of the owner". Most people just wanna be able to complain about it.