Live2d Cubism - Rendering MP4 animation takes so much time, no matter how high your specs are.

Rendering/exporting animation to MP4/MOV file takes so long no matter what your specs are! Turns out it doesn't use much of your PC's specs as it renders. I need it to render faster as to improve productivity, sometimes I also have deadlines to catch up, and it takes hours to finish one scene. This one scene I'm rendering has 3k+ frames, in 3200 x 2400 resolution in MP4 format. While rendering, it doesn't use not even 10% of my CPU power. It's nice to be able to work on something else while it renders, but sometimes I'm not multitasking, just waiting for the render to finish, which takes so much time.