Film grain is useful specifically in cases where you’re using lighting techniques that have to take a lot of expensive per-pixel samples. If you reduce the number of samples to save on performance, the value doesn’t converge and therefore you end up with random noise in your lighting output. Film grain is a compromise that adds random noise everywhere so that the noise in lighting is less noticeable, which looks even worse. Generally it’s combined with a sharpening filter that retains hard edges, but if overused it can definitely wash out texture detail.

Motion blur is useful in cases where you’re using temporal effects that gather screen-space data over several frames. These generally look great if the camera stays mostly still, but if the camera is moved a bunch you might end up with “ghosting” as the previous frames’ data is used for an incorrect camera position, and motion blur lets that data accumulate before the image is clear enough to spot issues.

Chromatic aberration is unlike those in that it’s not generally covering anything up, it is entirely an artistic effect. I think it can look pretty amazing if used subtly, but much like bloom it can very easily be overused and just get annoying instead. If you’re noticing the distinct RGB color banding at the edges it’s being used too much. But used right, it can give a lot of flair to bright lights, with a mild bit of hue shift at the edges.

I don’t like motion blur or film grain, I think they’re both crutches and look like piss, but to a dev team given limited resources to get a game out the door, they might be the crutch that makes the game shippable. Believe it or not, both of those effects look better than what they’re generally covering up. Games are all held together with duct tape and prayers under the hood.