IMHO, luck is only a factor in success. Failure is much more frequently pre-determined. For example, a startup with a great idea and a great execution still might fail, while a startup with a terrible idea or poor execution will almost definitely fail. I think of startups as needing to be not good but good enough: if the idea and execution are good enough, other factors start mattering. However, if they are not good enough, then no amount of luck will change that in the long run.

For example, the Color app had all the resources (funding, contacts), but the basic value proposition was just not there. They never had a chance. OTOH, Turntable.fm had a great product, but as luck would have it, they did not make it. Either the timing wasn't right or something else, but despite everything they are having to pivot.