In general you are correct, but there is the special case of a person using machine translation as a tool to try and communicate with someone they don't share a language with.
Of course, the first approximation is the person performing all the stereotypical monolingual behaviors of speaking extra slowly and loudly, using pseudo-simplified language, accompanied with exaggerated hand gestures that don't really help.
BTW, I've seen people struggling with voice assistants in almost exactly the same way (absent the hand gestures).
But the point is that people modify their language to try and compensate for communication barriers all the time, and it is just a skill, whether it is speaking to children, or foreigners, or code switching to speak to someone in a different class or subculture. Machine translation adds a new wrinkle to the mix, but it isn't all that different.
Which I did just yesterday by putting the text I wanted to convey into Google Translate and then tweaking it until the translation looked reasonable. In the end, I still had to postprocess the output a bit, but I ended up with something which I couldn't have written if starting from scratch, which was entirely worth the small pain of using slightly less colorful language.
I will generally run my English emails through machine translation back and forth multiple times until I find phrasing and word choices which are “bistable” (I get back the original English). I’ll also usually double check specific critical or unstable words using a variety of translation aids (not machine translation) to ensure any (scope-limited) Chinese I write is actually correct.
We do have one native Chinese on my side of the team, and every time I’ve had her check the Chinese she says it’s correct for our technical domain.
So we really are already at the point where we can communicate across languages with surprisingly low error rates.