Many customers need costs to be predictable and bounded. So a cost structure that depends on external factors is very rough on those at the margins. You can encourage many people to move to rate plans that depend on external factors, but not all.

And I'm not sure how your plan addresses the problem. Suppose I install enough panels and batteries for 48h of power. I only draw from the grid when there are 3 cloudy days in a row. If I pay by kWh, I don't really care how much it costs per kWh since I use so few of them. Yet I cost the grid operator just about as much as a normal customer since they need to maintain the capacity for that 3rd cloudy day.