1. "What got you here won't get you there." The problems that need solved today might require a different mindset/level of experience and that may not be in people with enough time or circumstances to build, or enough likeness to the old model be funded by VCs.
2. Distractions galore - Social media and trillions poured into the distraction economy ensures the ADHD-prone builders have less hours and are less productive in that precious 5PM-10PM.
3. Tech giants of the past 10 years were slurping the most promising talent with high salaries and burning them out.
4. Filters that sift new founders and hackers are created by people who don't deal with the problems most people deal with.
7. Hackers at hackathons are not dealing with problems most people deal with. A number of hackathons I've participated in had very similar solutions pitched - you could name the categories, and see them all over again in each hackathon years apart. Usually catering to the tech or the sponsors instead of actual products anyone wanted to use.