Fair play - it's good that there's choice and if it works for you, great. I also totally get the fun of building something yourself.
The local storage is a big one if you don't have a nas or home server on the network. Although, if you're linked into the *arrs then I would think most people already do. It's nice when new episodes just turn up automagically in Jellyfin.
I tried Kodi before but I found the commercialisation of it very jarring. Jellyfin is entirely free - your fifth point might give it extra credit for that. The Jellyfin app doesn't (afaik) feed any info to anyone, but you do need to load it from the Amazon fire menu, so you can't entirely skip their advertising. It is the only thing I use the fire stick for, and the price is cheap compared to anything else - it cost £25 and works on any TV. Being a dongle, there's no noise either.
Moved my stuff over a few months ago, ironically as a de-googling exercise to stop using Gdrive. :/