This is an interesting observation, not really something I have considered. The key difference here is that you are the one in control of those customizations. Whether the customizations are useful or harmful is entirely up to the user, Kagi just gives you the option.
For me at least, the majority of my searches I just want the correct answer to a question or a link to a specific resource I’m looking for. I don’t really use it as a content discovery engine. Being able to prioritize sites that I have found through experience to have reliable results and exclude sites that are uninformative or irritating is valuable.
I recently set up and started using MediaTracker for this purpose. It’s kind of barebones, but functional. Seems like its biggest difference with movary is that it also covers TV, ebooks, audiobooks, and games.
I have a little section for movies and books on my website and i’ve been working on a script to automatically pull those lists and reviews from MediaTrackers api each time I build my site.