Well in a very basic way, more solar than we can use means there is waste. Too many panels produced and installed. And if solar generation capacity is going to waste, that means Germany doesn’t have enough storage to keep it in, and that’s a problem. And who knows what negative energy prices will do to the other power producers who back up solar (which, you know, doesn’t produce at night). That would be a problem. So there is a little more to this than just the headline. Also, Reddit needs to learn that business stories are written for investors and business readers and they don’t frame everything in terms of broad human interest.
It costs something to build and maintain the infrastructure to distribute power. Typically that cost is recovered through payments for the generation of the power, which becomes a problem if generation costs get too low. It suggests that we should probably consider a different model of paying for that infrastructure now that the reality of generation has changed.