FWIW, Moonfin and Infuse both work flawlessly on an AppleTV.
I also remember Google TV working fine, but it seemed like ads got added to another part of the UI every month so I got sick of it.
Roku only supports text subtitles, so if you have picture subtitles (like a DVD or bluray), then you'll need to burn them in if you want to play on Roku.
The default jellyfin client works great also on my NVIDIA shield.
Young children and non technical adults can use it as easily as any streaming app. I guess you can tweak and theme it endlessly to look like your favourite streaming app but I haven’t felt the need to so far.
Self-hosting always involves a bit of jankiness, if you can’t handle that then back to overpriced subscriptions and spyware you go.
SenPlayer is also very good on ATV.