Well by all accounts it sounds fine now as its own community. The problems of everything riding on one main instance/set of maintainers would be a problem in the future.
Things have not always gone well on the Fediverse and Lemmy, but we have been able to get through these problems thanks to the safeguards of federation and open source. E.g. Feddit.de broke and the original owner was nowhere to be found, but feddit.org was able to succeed it.
Even if Mastodon and other Fediverse platform gains are 1% of the gains of BlueSky or anything else, it’s still cause for celebration and to welcome new friendly faces with open arms.
When the Reddit API-calypse happened, I don’t think anyone expected Lemmy to have more users than Reddit or anywhere even close to a similar number. But Lemmy.ca went from around 40 active users in April 2023 to hundreds, and then to 2k over 3 months, most people being friendly and ready for something different.
Quantity isn’t everything. There is an innumerable amount of things that could be better about Mastodon, Lemmy and other Fediverse software and sure, mass-adoption could help with niche content. However the way the Fediverse is set up, it is resistant to all the sacrifices other platforms had to make in the long run to be more profitable. Musk-boi could “buy” Mastodon, Spez could “buy” Lemmy.world and ml, and Zucker-bot could “buy” Pixelfed tomorrow, but that wouldn’t stop anyone from forking those platforms and leaving the main instances. The distributed nature makes it hard for a monopolist to capture.