If you are okay with not hiring the best, then sure, move your startup to Phoenix. Startups go to Silicon Valley and NYC because that's where the talent is. Talent goes there because that's where the startups are. Even if everything about Phoenix is objectively better, how are you going to overcome this trend?
Real talent goes (or stays) wherever it damn well pleases, and has the leverage to insist on telecommuting if that's not where HQ happens to be. "All the talent is in X" is egotistical BS for any value of X, whether it's a city or a whole country.
There are way, way more talented people, for any level of talent, in the bay area than in Phoenix.