Personally, I think I initially leaned towards "building something cool" - which led me to build something which "I" thought was cool only to realise later that

Personally, I think I initially leaned towards "building something cool" - which led me to build something which "I" thought was cool only to realise later that there aren't that many people sharing my same thought. Above leads to an unprepared development of a product because you don't know whether there is a need/problem out there. I think that's why it's so important to know the market + customers. I think if you do find a problem to solve, then you can build something "cool" to solve that problem. But if you have to compare the two, "solving a problem" seems objective, whereas "cool" is... just... too relative + subjective.