You want to talk about unrealistic command assignments in Trek movies? Let's see... how about dropping Admiral Kirk back down to captain and demoting Captain Decker to first officer for the V'Ger mission, rather than just having Admiral Kirk lead the mission with Decker's Enterprise as his flagship? How about giving Kirk & crew their own replacement Enterprise after they committed mutiny, sabotage, violation of restricted space, and the reckless destruction of Starfleet property? How about keeping the same command crew together in the same posts on the same ship (or its replacement) for over a quarter-century even after they've all reached captain's or commander's rank? We've already got plenty of precedent for Starfleet making command assignments in ways that by modern standards are quite capricious and illogical.
Promoting Chekov to commander in the first place was pretty silly - the guy was an air-head.
But yeah, I think Decker would have filed a grievance with his union rep had he lived through the V'Ger incident.
Having the crew training cadets in TWoK was fine, putting the senior crew at comms and helm instead of the cadets they were trying to train was pretty silly, at least until the crisis erupted.
Given the hard time Kirstie Alley felt she had I think it was more the actors worrying that they might be replaced that led to the silliness.