Evening,
So I had this very same problem with textures loading slowly or not at all on buildings, objects, etc. as well as notable overall deterioration of graphics.
If you are like me and put your PS4 mostly on rest mode without closing the application, aka leaving the game running, it seems that this issue manifests itself and gets worse over time. Is it a memory issue or what, I don’t know, but first closing down the application, and then restarting the PS4 did the trick for me. I tested this very basic method with save at Rattay (which at the time looked like a bland mess of missing textures and geometry) and it worked wonders! Also landscapes further off got enhanced a lot.
This was tested on PS4 pro, latest update applied as of 18-2-2018.
Now, texture pop in still occurs, but it’s far more gradual again.
Other than that, on my first night while I put the PS4 on rest mode while the game was running (pause menu), I noticed in the morning that “time played” had increased somehow by the time I was out. Hasn’t happened since, but it led me to believe there is something broken with the rest mode and this game.
Hope this helps, and please share whether you get the same results or not.