My heuristics is that the first 100 users are almost always a distribution problem. If you do not have 100 users using your product extensively, and you see a retention drop there is no way you can conclude anything else.

The reason why I take this approach is that - I have had personal experience building tools that didn't go anywhere, and same tools built by people with some online following gaining good traction. It could simply be a case of anecdotal experience, but distribution has always been harder for the tools I have built.