Most of that stuff isn't necessary just to replace Plex, the OP's saying them Jellyfin started them on a journey they're presumably enjoying, not that they needed everything there to replace it.
I think you're right the bar is still too high for most folks, although I will note that I think it's dramatically lower than it used to be. A lot of the tools are all-around way easier to deal with, tailscale makes a lot of "personal cloud" use-cases much more feasible, and then coding agents (I'm using claude code) dramatically reduce the labor costs of getting this stuff all working and fixing it when something goes wrong.
It's not that postgres can't handle large tables, it's more that many of the ways it uses system tables aren't particularly optimized for them being large, so you're operating outside the territory the table/query design was probably built for.
Like most things postgres it'll probably still work better than it has any right to for a while, but it'd be extremely unsurprising if it caused you unexpected problems at some point. (And if it does, they'll likely excitingly novel and you'll probably have to dig pretty deep to understand what's going on.)
I think you're right the bar is still too high for most folks, although I will note that I think it's dramatically lower than it used to be. A lot of the tools are all-around way easier to deal with, tailscale makes a lot of "personal cloud" use-cases much more feasible, and then coding agents (I'm using claude code) dramatically reduce the labor costs of getting this stuff all working and fixing it when something goes wrong.