Yes, and: Parties get candidates elected. It's a form of social validation, vetting. The alternative is more money (buy votes). Everyone should run for office

Yes, and: Parties get candidates elected. It's a form of social validation, vetting. The alternative is more money (buy votes). Everyone should run for office at least once. Folk theories don't jive with the reality. Yes, and #2: Polarization != partisanship. Factors outside of the parties begat our current polarization. Ezra Klein's Why We Are Polarized is a good primer.