I’m having the same issue here as well.
I’ll be honest, I was beta testing Shadowlands and thought they hadn’t finished it!
My motherboard and CPU are pretty old, but up until Shadowlands I’ve had no issues with textures at all.
CPU - AMD A8-3850
Motherboard is Gigabyte GA-A75-UD4H
Graphics card - Nvidia GeForce RTX 2080 Ti
Samsung SSD 860 EVO 4TB hard drive
I’ve not felt the need to upgrade my motherboard and RAM as the machine runs all games, including the previous version of World of Warcraft BFA perfectly fine.