This is from someone who never uses the ATV app, other than for ATV+ content. We’ve used the wish list in the Movies iTunes app for, I don’t know, 13/14 years. Logical you browse and save your bookmarks in the single app, no need to flick over and add it to the play next. Of course this is why Apple are now pushing everyone into the ATV app and that’s fine, saves confusion.
The main thing I dislike The ATV app is the clutter, especially now they’ve mixed films in with TV shows. Too much distraction when trying to pick something specific. I hate video playing when opening the home page, get sick of seeing the same sequence with no option to toggle that off. It’s all got a bit Netflix like, but even they have seprerate section for movies, as do all the other streamings I can think of. All this genuinely puts me off browsing for movies as I have no interest in TV shows really.