It makes grid planing an absolut nightmare. We need to overbuild by a lot so a few days with less wind and sun doesn't lead to blackouts. Big windparks can be turned off reliably if there is too much energy produced, but the same can't be said for personal installations.

While it's possible to disconnect personal solar cells from the grid by increasing the frequency a bit, you can't just do that if the village is still connected to the entire grid. You first have to switch the whole village manually into island mode. Not to mention that a lot of times they don't restart automatically.