Very slow Viewport animation, but system is not overloaded

Hello Everyone.

I have dual CPU motherboard Xeon E5-2678
4k Dell Display
Win pro 10 64, Blender 2.9, Blender 2.93 x64

Final render for Cycles and Eevee works pretty fast
When I run animation in 3D Viewport, also in Solid Mode
More less simple scene - Low Poly, no hidden Modifiers
50K faces for 21K Objects

FPS is around 6…

But My system CPU Utilisation is only 8%, and 40% for GPU

I tried to find something in internet - Nothing with similar case.

may be someone faced with that issue? may be exists some specific configuration options which allow Blender to use more resources?

what happened at the end? did you end up solving your problem? I think is because of your 4K display, it takes more memory and bandwidth from the GPU/CPU to render your workspace, there is an option where you can change the resolution of your viewport