I still see the occasional person on Twitter say that Mastodon will never "succeed", but I wouldn't call what Twitter has "success". Mastodon is good ol' community building.
We don't want to be exhausted by brands and promotion, nor have the platform continue to be unethically designed and lack any backbone for moderation. Federation spreads out the moderation task and the lack of brands and promotional nonsense is good. We can just follow and talk with others which is all people really need.