I wouldn't be too worried about Threads joining the fediverse.

They had the perfect opportunity to dethrone X with a superior app but have given users the most barebones piece of shit that doesn't even have support for hashtags or trending topics.

Mastodon has this functionality.

Last time I booted up Threads, my feed was flooded with e-girls posting twerking videos. I don't follow any such accounts on Threads nor Instagram and I don't like it when my social media feels like a softcore porn platform.