More like it was a movie that could have been b-grade but was instead was good enough to be A-grade. I think even crew thought it was going to be a B-movie actually. Not that B movies are bad of course.
Alien's characters doesn't do anything nearly as stupid as covenant characters.
To compare the more stand out ones.
Kane vs Oram.
Kane was in a suit and had no reason to suspect anything as things looked long dead in the derelict. As far as he knew as well, the inside of the derelict had the same atmosphere as the outside, meaning he probably didn't think somethign would just jump out unimpeded. His personality was established via some dialogue. Doesn't excuse his foolishness though, caution should have still been followed but at least there is more to justify it.
Oram just experienced the threats the pathogen-generated creatures pose and David outright tells and shows him their origins. He then shows him the "successors" i.e the same type of infectious parasitic creature that killed his crew but more advanced, and he sticks his head into something because an android told him too.
Brett vs Rosenthal. Brett thought he was still looking for something small and because he let the cat escape, he was told by the others to find it, also he was in a ship he knew well. He didn't expect an 8ft tall monster to be roaming around. Again still foolish but not as bad as Rosie.
Rosie saw what the Neomorphs did, how dangerous they are and that at least one was still roaming about somewhere.
she was is in an unfamiliar area with the outside area filled with corpses, yet she decided to go off alone just to clean a wound that a simple first aid kit could have done. At the very least there should have been a buddy system. Two people at least to watch eachother's back.
Then you got that character that near enough shoves his face into a spore pod thingy.