I don't agree with that take. I'm quite happy the celebs are not on it. It's about appreciating nice pictures, the way Insta was in the beginning. I'm quite okay without the endless self-promotion packaged as insights into their lives #ad see link in bio crap.
The fediverse as a whole will grow slowly but steadily and one day in the future the trend will come to us. Whether it's run on Mastodon, by extension Pixelfed, Bluesky, or something new.
I also don't think that if, hypothetically, today Taylor Swift abandoned corporate social media and started posting on the Activity Pub branches, this would move the needle much. Yes, a bunch of people would sign up for accounts out of curiosity but they will just as quickly abandon those. Because most people are not used to or are willing to invest the time to craft their own timeline and thus grow bored. The bigger hurdle is ease of onboarding, not lack of a-listers.