To me, it was two things:

1. As a Twitter replacement, it solved the wrong problem. They seemed to think that the flaw with Twitter is that it's free. In my opinion, the flaw with Twitter is that it's centralized.

2. Every time I mention how the Twitter replacement isn't compelling, people would talk about how that's not what it is, it's a general platform for Stuff that just happens to be something you can use to build a Twitter replacement. But they never really explained what it was, just that it wasn't merely a Twitter replacement.