If the argument is "communism bad because people died" and the alternative is a system that also leads to people dying, then it is a defense against the notion that the current system must be maintained.

Now, if there are other systems that are even better, great. But usually when people trot out the "communism killed 27 kajillion people" argument, they are using it to argue that capitalism is better.

You agree context matters I assume? In the context of addressing deaths caused by ML, saying capitalism causes deaths too sounds very much like an intended defense.

That being said, every political system ever has caused deaths, whether intentionately or not, so it's a moot point anyway. I hate arguing it. It's much more relevant to just say capitalism's falling is actually the intentional fueling of inequality through false meritocratic rhetoric, which results in death and suffering due to not affording vital necessities, class tensions which result in a more divided society, stifling human progress by focusing on what's more profitable instead of what's better for people as a whole, so on and so forth.

So no, I do think it's an oversimplification that doesn't even touch the problem, since it's a trait it shares with all past political systems, and perhaps with future ones as well.