Setting up a reverse proxy and dynamic domain is not one click
Maybe not for the server administrator, but for users, it's mega easy. Download Jellyfin app on TV. Enter URL for server. Login like a normal streaming service. Done. As far as I know, Plex requires these same steps, so if Plex works for your 89 year old grandparents, Jellyfin would as well.
Jellyfin has also yet to resolve the unsecured api
In what way is the API insecure? What types of attacks are you concerned about?