If the market is being driven negative then it means there's an oversupply. Which means overall the price of electricity is higher then it should be - negative prices have to be compensated by higher positive prices at other times, and reduce the return on capital to build new power infrastructure of all sorts.
Turning off productive solar panels is wasting power.
The negative price can also be thought of as paying people to use the productive solar panels rather than turn them off, it's a two sided market that drives demand to times of clean and cheap energy, which lowers costs for everyone.
Turning off productive solar panels is wasting power.