I think not being able to search for <random celebrity> is a good marker of how mastodon is trying to be something other than just a decentralized twitter clone.
I personally find the twitter microblogging model, wherein most tweets seem to be retweets of high-profile users or comments on their posts, quite unhealthy for discussion among equals.
Twitter is essentially a media site, whereas (I think) Mastodon hopes to be something else, more of a forum for actually taking to people. Whether it can work as/if the userbase grows remains to be seen, but I'm cautiously optimistic.
The other thing to keep in mind is that idiosyncratic norms and conventions pop up that are products of how people use the platform, and these have a way of turning problems into non-problems.
Maybe the network will just evolve to value interactions that aren't centered around brand pushing. Maybe it will let the rest of the social ecosystem take care of that and meanwhile mastodon will do it's own thing.
Or maybe a mastodon instance will seek to distinguish itself by providing this kind of verification and become the de-facto instance for verified brands. (There's already a mastodon that explicitly courts business brands.) Maybe we'll even discover that we just don't value such a thing that much, when it occurs on a network structured to make it easily separable from the rest of social activity.
All of which is not to say we should waive away the problem, only that it need not be a conversation-stopper when it comes to the question of whether mastodon has offers "enough" value in its current form.
