I sympathise.
In the old days of ATV1 with a large internal disk you could simply sync a huge bunch of personal movies, photos, CD-rips. A hobby product that simply worked for family use.
The internal HDD went to favour "modern" cool streaming supported by a poor AppleTV remote app, followed by a crap ATV4 physical remote with a user-UNfriendly ATV Computer app that crashes when you launch a basic photo slideshow.
Playing personal/family media has become a nightmare. Today everything is centered on AppleIDs, DRMs, cloud and subscription services. There's no iTunes home media centre that can plug into the ATV & homepod environment. A basic shared "family" iTunes media centre is a real pain to set up in Apple's world ... there's not even support for a basic 2TB SSD plugged into the back of the ATV.
The only real option pushed by Apple is forcing me (and the rest of the family) to sign up for a monthly fee to stream my personal content from a cloud service ... and then hope to tie me in to purchases.
I have my content and don't need to send data around the world to get access to it. Pay to waste more energy in storage systems and data transmission between server rooms ? No thank you!
Patience running out and will be spending time re-assessing plex and getting rid of the Apple environment.