There are very few companies whose idea I initially thought was useless that have ended up going big - twitter is one of the only ones on that side of the spect

There are very few companies whose idea I initially thought was useless that have ended up going big - twitter is one of the only ones on that side of the spectrum. Sure, they may have some issues that need to be overcome, but for the most part, the ones that have gone big have a very obvious core appeal. If everyone thinks it's useless despite understanding the crux of the idea, I think that's a really, really good sign that you need to go back to the drawing board.