Ask HN: Passion vs Execution

Is start-ups all about execution and not passion, when we were looking for new ideas to build a startup, we got tons of them, but 10 startups(global) were already working on it, so we dropped the idea and moved to next and kept doing this till we ran out of ideas. The CTO of a startup where i turned down an offer (not passionate about the idea) also said, being passionate about the idea helps for a few days, but after than it all boils to execution and the daily grind.

Would like to get your thoughts on it.