There's a lot of difference -- i.e.work -- between a CRUD app and a successful business. The experience has shown that the first version of anything is rarely successful; it's only after a lot of testing and tweaking that you find the right formula (and then you still have to keep working on it).

Anyway, an idea that a) has the concrete people with a concrete need, b) can be (at least initially) solved with a CRUD app and c) hasn't been (successfully) tried before is so rare that you probably have more chance to literally stumble on a buried treasure. Of course we would all like to have an idea like this, but the problem is that you can't possibly know that you do until you execute and test it -- in nearly all cases it will turn out that you were wrong on b) and/or c) above.