If the vast majority of Americans believed the Democrats to be less evil, the Democrats would have 90% of the vote. If that were the case, the Republicans would move ever further left, perhaps even overtaking the Democrats, until they get a chance at winning again.
The reason the parties are right wing is because the voters are right wing.
That's why we need a communist revolution where everyone will be a happy little comrade
The reason that people don't vote Democrats is the same reason that people won't join your revolution.
If you found enough people to support a revolution, that'd mean you have enough people to change the system by simple voting.
Another upside is the easy permission management.
You can revoke network access from your password manager to reduce attack surface; you can revoke camera access from your chat app to prevent accidentaly enabling it; You can restrict an app's file system access to prevent unwanted changes; etc.
It's not yet fit to protect from malicious apps, but it still finds some use.