I'm skeptical of any food that humans only started eating since the industrial revolution, including those that are derivatives of or isolated compounds of real food. Mostly the effects on our bodies are not well studied. I haven't specifically read studies on msg though.
I mean, foods like soy sauce and yogurt and sauerkraut predate industrialization, but are very processed. I wouldn't worry too much about MSG in particular, since it is also mostly made by fermentation:
