Yeah, step one to building the next Trello is be Joel Spolsky, or possibly 37Signals; failing that, be [otherwise] exceptionally good at marketing and generating goodwill. Because the reality is that "it's simpler to use, more general and has less bloat than the market leader" is not a unique selling point, it's something pretty much every new entrant into a market achieves by default. So you have to do a lot more than that for your KISS general productivity/collaboration app to stand out, particularly if starting from the significantly disadvantaged starting point of not being Joel Spolsky