I saw some reasonably interesting Fleets at first, but it quickly devolved into a low-effort self promotion feature as they noted:
> Although we built Fleets to address some of the anxieties that hold people back from Tweeting, Fleets are mostly used by people who are already Tweeting to amplify their own Tweets
Eventually I stopped clicking on them because I knew I'd see the Tweets during my normal scrolling anyway. I suppose this problem is inherent to Twitter, where Tweets are already low effort enough that they didn't need another feature for rapid-fire, low-effort content. Contrast with Instagram where people's posts are generally well thought out, but their stories are made for rapid-fire content.
Twitter didn't have the same divergence, so Fleets and Tweets became the same content in different formats. And of course, the Twitter self-promoters took full advantage of a feature that let them bubble their content to the literal top of people's feeds.