If there's anything wrong with MSG that isn't simply due to sodium intake, I think it's unknown to science (at least in the sense that there's no theory about it with any wide uptake). MSG is also intensively studied and has a very similar mechanistic story to aspartame.

Sure, but it feels like a silly distinction. The famous example is water, which fits those same criteria. Would we that that there's not "nothing" wrong with water?

What's wrong with it?

And water