I signed up for Twitter more than 14 1/2 years ago and for me it was the most beautiful and above all the most useful form of a social network. Not only could you follow interesting people or fun accounts, but you could also follow bots that flushed important tweets into your timeline. I have never used the web interface, but have always used Tweetbot as a client on all my systems. An excellent piece of software and it is hoped that there might be a Tweetbot for Mastodon in the near future.
But for me, Twitter is the end of it. I'm quite inconsistent and won't delete my account for the time being, I have to process the pain of my separation first. ;-) But I definitely won't post anything there anymore, or even feel the urge to miss something there. Too much has changed there in the past few weeks in terms of the apparent alignment of the network. If it is now possible for the boss to personally conduct surveys on his account (and thus his filter bubble) about far-reaching decisions, that is no longer consensual for me.
Mastodon feels quite nice, the decentralized architecture gives hope that no power structure can arise that could endanger the entire network. We'll see.