If you pay a fixed price for the grid then your price per kWh goes down and it makes less sense to put solar panels on your roof because they need to beat the lower price per kWh unless you can get entirely off the grid.
But then you do have the incentive to get entirely off the grid if you can, because it gets you out of the grid attachment fee. So it justifies more in the way of batteries to avoid that cost.
In other words, it makes solar + grid attachment unprofitable, so your viable options become full grid or full independence. Then depending on which one has lower costs at scale, it either ends rooftop solar or ends the power grid.
And that could go either way. The power grid has economies of scale, but it also has transmission costs that don't exist for local generation, so which one wins?
It's residential users who usually don't have a split bill like that.