For many years, I've ripped all my DVDs, Blu-Rays, and HD-DVDs into my computer, and it's great to be able to watch any of my digital content on any of my devices whenever and wherever I want, without having to have a huge stack of discs laying somewhere accessible (I store them all in a box in my basement).
For almost as long, I've used iDentify for this purpose, but it looks like the developer behind the app gave up on the iTunes/macOS ecosystem entirely in the past year or so, and the app stopped working on macOS Sierra 10.12.
I looked around for alternatives, and found mentions of iFlicks (didn't seem as fully featured), Vidalin (no longer developed), MetaX (no longer developed?), and Subler. I tried a couple of these and didn't find them as pleasant as iDentify, but then I also found MetaZ, tagged as "Two letters better than MetaX".
MetaZ is basically a continued fork of MetaX, and so far it's been working very well in my testing, though it's not nearly as good as iDentify was at automatically retrieving metadata.
IMO, the most annoying thing is the fact that I can't tag videos like I do songs and audio files within iTunes... you'd think Apple would've fixed that by now, but go figure.