However: I have many ideas, but don't know which one to throw myself behind 100%. I can execute well, and in my day job I am executing all the time for somebody elses business. Why don't I make the jump and become an entrepreneur myself? Because I don't know which of these ideas are actually any good - in the sense that they have "market fit" and somebody willing to pay for it. And even if you have a potential market, the barrier to entry is often ridiculously high.
So far, I have not found a single idea that is actually viable as a business for me.
I have a lot of great ideas: A new kind of calendar app; a new declarative plotting library that uses CSS; a friend-of-a-friend P2P app that piggybacks on your existing contacts; smart light switches that physically flip when you switch them remotely. If I pour myself behind any of those, I'll make a great product that people will enjoy but I will likely end up broke because none of them is a viable business.
Now if I find a novel problem that I can solve - lets say a friend tells me that all municipal governments really need a certain app to track tenders or potholes or daycare slots and are willing to pay for it. Or I can use some obscure thing from my studies to fix a big problem in an industry. Then this idea becomes really valuable. I'm never going to be the only person in the world to be able to solve a given problem, but I can be the first. The execution is secondary, because a lot of execution is mediocre, and you just have to be good enough. The opportunity is everything.