[2019] The game takes up 90% of my GPU on the menu page after disconnecting from the server, and 50% of my GPU after just launching the game, Why does the menu use up so much of my computers resources?

Because you're bottlenecked by your CPU, the CPU doesn't need to do much so you're able to render more frames increasing the load on your GPU.

It's best you limit your FPS to your monitors refresh rate.