In some ways, yes. In some ways, no. A huge portion of BookTok "success" is a) people who were already very successful, b) traditionally published authors (who were already popular), and c) people paying influencers to post about them).
Sometimes a mix. Word has it Colleen Hoover's publishers paid 100s of thousands to influencers to achieve her new wave of success, but she was also already a very successful traditionally published authors.
There absolutely are authors who are finding success with their posts. And there are, no doubt, some authors who had smaller followings who exploded because BookTokers stumbled on them (though I don't have any names of people who weren't already rather successful).
But... this is picking up new readers and driving a lot of paperback sales/ sending readers to bookstores which really need the traffic.
I still don't see a great way for authors to really utilize TT for consistent success. You can get a video to go viral, maybe, but that doesn't mean your next video will do well (or sell books). I did see a small boost when I had a video do particularly well (about 10k views) but it was only a small bump, and if I did the math for time ROI, I'd be making $2/hour, at best. (Not to mention losing tons of headspace to thoughts of TT. Like all social media, it's very mentally stimulating).