For 1, 2, 3(?), 4, you appear to be referring to the Apple TV client, which is written in an entirely different language and frameworks, and entirely different authors. (This is due to the excessive limitations on languages put in place by apple in their ecosystem).
Jellyfin has dozens of other platforms.
In regard to #3, Jellyfin does use file watchers.
For #5, there is a setting to grab trailers. Additionally, if the default metadata providers aren't getting you what you want, there is a baked in library of more than a dozen alternative metadata providers and a variety of other things you can use to augment what your media library provides.
For #6, I'm not sure if you're just referring to the Apple client again, but I'll add that the "Jellyscrub" feature is turned off by default, but if turned on, it will automatically generate video scrub images.
For #7, idk. I guess it's a stylistic choice? Why is there Sonarr and Radarr?
Anyway, I'm just a user, but, I'm also a Jelly-stan. So, I'd highly recommend you browse through the configuration options a bit more, particularly in regard to plugins and the many settings available in each of libraries' individual configurations.