They made changes so that a nearly 20 year old game can keep up with quickly evolving technology. You could literally do a /console command and have it fixed yourself until blizz patches it. Kinda silly to get this mad over something that takes you 2 seconds to fix.
/console SET GxAllowCachelessShaderMode “0”
You can also uncheck the background fps and target fps to fix it further.
The changes they made are so the game relies more upon your vram now instead of your cpu.