The alt social media are a good place to run away from algorithms and explicit mass manipulation from other big tech, be more free, independent, and spread ideas, but I also think that the fediverse is being filling with people with radical political ideologies, some kicked out of traditional social platforms for this same reason. I’m not saying that we can’t have discussions, but I think that many people are making their own echo Chambers in the fediverse.
I fully consider unsolicited commercial advertising illegal (it’s theft of resources, if nothing else), and it’s happening on Lemmy plenty.
Not sure where one comes to the conclusion that there’s not much we can do to stop it. There’s varying levels of responsibility around managing an online service, and there is much that one has to do to keep on top of it, lest their instance turns in to a cesspool and blocked out of existence.