But users are not mindless drones. Even the least computer-savvy is aware that they're being asked to make a choice and is probably unpleasantly reminded of the dark patterns in user agreements etc., so they'll feel like they're being guided down a sales funnel immediately after installing the app/signing up on web.
What percentage bounce at that stage? It's probably large. I did so, and although I later relented and created a Mastodon account I've felt emotionally biased against it ever since and barely use it. When I have used it I don't experience any tangible benefit to overcome my reflexive dislike. The network effects aren't anything great, the timeline/feed mechanism and presentation are not fundamentally different from other social media offerings, the QoL improvements are marginal. If I cared about architecture and ideology above all else it would be great, but what I actually care about is being able to get news faster than any other source and being able to find more people there than anywhere else. I can only think of 1 or 2 people who I check in on periodically via Mastodon because there's no other place to find them.
