When you have 100000 small producers (assume everyone in a bigger area has photovoltaics on their roof), then suddenly stabilizing the frequency becomes more challenging, because everybody has to work in exactly the same rhythm.
That's why you have standards and codes, that ensure everybody's equipment is capable of syncing to the grid properly before they are allowed to connect. It's not that hard for an inverter to do. Then you have the constant background supply to stabilize it like battery farms and other energy storage technologies. And a bunch of capacitor banks to correct power factor issues.
I don't think we are getting away from centralized production anytime soon. Even with the move to wind and solar, although I think nuclear should be included in that mix.