That isn't the limitation though, it's the consequence. The phrasing of the tweet is extremely memable, but thinking about it for 5 seconds should make you realize that negative prices mean they REALLY need to get rid of it. Because having too much energy in the grid is a problem.
The negative prices indicate instability in the whole energy system, that's not necessarily a capitalism thing. Don't get me wrong I hate capitalism and love sun and wind energy, but many people are ignorant about the fluctuations and the fact that energy storage is not a solved problem right now.
But the original post doesn't say "it is unstable and has a problem of storage" but "it drives down prices"
No matter the reality of things, the post is concerned by the very capitalistic issue of making money out of it. It might not be the main issue, but it is for them.