I recently got around to watching X-Men: Apocalypse, and it is indeed a big-budget mediocrity. Setting aside the fact that structurally it should have begun about halfway in, one of the things that often seemed jarring was something for which I have no name, but which might be called its filmlook.
By 'filmlook' I don't quite mean the look of it, and I have difficulty pinning down precisely the difference. But perhaps it can be conveyed by example. Almost any decent-sized budget science fiction movie produced today will have aliens, ships, and the like, with a better look than you can find in the 1953 War of the Worlds. But this doesn't usually translate into better filmlook. The 1953 movie, which won a very well deserved Academy Award for visual effects, has an integrated aesthetic with a coherent and balanced set of visuals, and the ships look very good in the context of the film. Any hang-ups about realism occur well outside the experience of actually watching the film.
We see this also with horror movies -- the monsters today look a lot better as monsters, but this doesn't always mean better filmlook, which often gives us the paradox of more realistic monsters looking more fake, or things that would be more scary in real life coming across as much less scary. In zombie movies, for instance, the old-fashioned slow zombies, for all that you can make fun of their snail's pace, consistently have a better filmlook than more modern swift zombies; the former allow for creepiness, but the latter only startle. It's often the reason why less-is-more is so important for horror and the like -- one good scene with great filmlook is worth a thousand scenes, however impressive visually, without it.
The visuals for Prometheus (to use a franchise with an SF-horror blend) were stunning, but if you compare it to Alien, where the visuals are often less impressive in themselves, the latter has better filmlook almost across the board. This is obviously true of the alien-monsters, but in fact once you recognize it you start noticing it throughout even in things like how rooms are set up. The earlier movie has visuals that are often deliberately dingy and sterile, nothing impressive to look at compared to the lush and weird novelties of the latter, but they make a real contribution to the entire movie and 'fit' better. The distinction is easiest to see with monsters, but it's really about the visual role of something in the larger spectacle of the movie.
In X-Men: Apocalypse, the filmlook is very uneven. The Quicksilver scene has both brilliant visuals and excellent filmlook -- really, at this point, one almost the X-Men franchise should just have a movie of Quicksilver repeatedly saving the day -- although one could perhaps argue that while it tops the Quicksilver scene in Days of Future Past in look, the latter still trumps it in filmlook. But most of Apocalypse has very poor filmlook despite have impressive visuals -- the aesthetic is mish-mash, the choreography of the big fight film often comes across as fake, the impressive visuals often don't really do anything for the scenes of which they are a part, transitions from visual to visual are sometimes jarring in a way that disrupts the story rather than furthering it, and so forth.
Good filmlook won't always save a film. Oblivion is an example of a movie with excellent filmlook that just comes across as flat overall -- it's a movie, I think, where it's hard to point to anything that was done wrong and yet somehow it doesn't really stick with you. But in a visual medium, getting the visuals right for that particular use of the medium is going to cover a lot of sins. And not getting them right in context will sap most of the value out any spectacle, however impressive it might be in itself.