A lot of developers work really, really hard on their 
  startups for years bootstrapping, just scraping by, and 
  being ignored by investors because they're not famous. 

Their startups have no users and they are just scraping by because they are terrible at marketing, or at knowing what people want. Achieving a low cost-of-customer-acquisition is a real, quantifiable skill.

There are basically zero hot startups that have problems raising money. Getting to "hot" is the hard part, and it is not just making something, but making something people want. Good promotion is just as much of a skill as good UI design.