What It Isn't

In solving a problem of this sort, the grand thing is to be able to reason backwards. That is a very useful accomplishment, and a very easy one, but people do not practise it much.
- Sherlock Holmes, A Study in Scarlet
Sometimes we're so confident in our product (its capabilities, its benefits, its value) that we end up sounding like a greatest hits album with nothing to separate us from every other album in the category.
Or we're so complex that we throw the entire kitchen sink at our audience, and they get lost, unable to distill what we actually do for them.
Similar to approaching something like a beginner, or using the "yes, and" principle to open up new creative directions, sometimes you need to let go to grow. Not by scrapping your solution, but by looking at it from the other end.
Define what you are NOT.
Can you differentiate yourself by listing what you don't provide, the audiences you don't serve, the value users shouldn't expect from you? What is your startup, in short, simply not?
In the beginning, that list is easy and long. But as you dig further, the value proposition gets slimmer, more refined, more focused. Less is genuinely more here: it gives you and your audience something to orient around.
Yes, you might shrink your apparent audience size. But that focus lets you reach your ideal users more precisely, with clearer messaging and a sharper value proposition.
Sometimes the clearest way to define what you are is to start with what you aren't.