Gabor Cselle writes about the lessons from Twitter alternative T2-Pebble not making it.
For me there were two flaws. He mentions both.
First, not getting an app out to the market. The web interface was fine in itself, but not the best way to consume a feed.
Second, not joining the Fediverse and providing access to a wider range of accounts and ideas.
In practice I found the small community was friendly enough, but there was close to zero focus on anything I care about.