1. Threads federates
2. Threads hosts 99% of all content and all users.
3. Threads releases and update that allows a new feature. Example: they add buyable threads gold, that you can reward to a post or comment.
4. The rest of the fediverse can’t implement this feature, and is inherently left behind in terms of features.
5. Threads releases an update that breaks federation. 99% of the users do not notice.
6. It takes Threads 3 months to fix the issue.
7. Go back to step 5.

Every non-Threads participant will have less features, and is constantly struggling to keep up with the changes and bugs of Threads. Result: the fediverse cannot grow. Only the most stubborn anti-Meta users will accept the objectively worse experience, just to avoid using Threads. But the average user will just use Threads, instead of joining Mastodon, Kbin, Lemmy, or any of the many other fediverse instances that Threads can federate with.