Otherwise, I would be consumed by PQ-issues instead of just enjoying the movies themselves.
I feel you miss the point, if image quality doesn't matter then why don't we just all go back to watching VHS, why didn't we just stick with DVD, another point is that for myself and no doubt others, we have seen these films multiple times and enjoyed them in the past, we can enjoy them again on blu ray but that doesn't mean they are immune to criticism and it doesn't mean people can't point out severe issues such as the lack of film texture on one release and too much sharpening on the other release.
Many things can take a person out of the film, the bigger the screen the more you notice edge enhancement and lack of film texture but even on 50 inch sets it can be an issue, i sometimes get taken out of a film by CGI which looks so unreal because they give us camera shots using the CGI which change the laws of physics and my brain tells me something isn't right, edge enhancement really annoys me, just as much as pan and scan on VHS annoyed me back in the eighties/nineties.
It would be great to just enjoy the film, i can do that with Ben Hur, Lawrence Of Arabia and a number of epic classics because they did a great job with them, they may not be perfect but they are good enough, unfortunately Zulu isn't good enough just yet, maybe one day they will get there. There is a certain quality level that i personally expect with blu ray these days.
I would think people on specialist forums are the ones who complain, i often read Amazon reviews and the 5 star review where the person notices nothing wrong with anything he buys ( unless he is complaining about film grain), they see boosted contrast and overly saturated colours and think it's great, that's what happened with the first release of Zulu, many 5 star reviews on Amazon.
We are all the more educated about films these days, our expectations are higher based on what we know is possible if a decent film scan, light handed cleanup and great encode is made, so yes a poorer release can pull you out of a film, if i didn't care about the quality i would just stream the film or stick to the DVD, my tolerance level is lower because if it wasn't i would not have bothered buying into the blu ray format or indeed any format, i'd now be streaming every film i watch since PQ wouldn't matter.