Well, I said that it had been 'done', ad nauseum, but I don't have any special insight as to whether or not it's been solved, or that even if it has, that there

Well, I said that it had been 'done', ad nauseum, but I don't have any special insight as to whether or not it's been solved, or that even if it has, that there isn't room for improvement, or differentiation. Search was considered 'solved' well before Google got into the market, for example. That said, I'm not aware of any such lists, though market research is always encouraged before spending time on development.