Yep, absolutely. But in reality there aren't that many brilliant developers who can do both with skill and you are lucky if you can find them AND convince them

Yep, absolutely. But in reality there aren't that many brilliant developers who can do both with skill and you are lucky if you can find them AND convince them to join you. To attract those, you're going to have to have a big offer (both remuneration and the nature of the startup) to attract these folks. Another school of thought is find back-end devs that can do some ops (although yes, it's ideal to have that as a separate position if possible) and front-end devs who can also do UI design and usability. You will need these two hats too.