GPU usage always at 100%

Hi, when I play the game my GPU usage is constantly at 100% - but only when I am at ground level,
when I go to basement it falls to 'just' ~55%

I have enabled DirectX and put all the graphics to maximum,
also I have pretty decent GPU:
GPU NVIDIA GeForce RTX 3060

I mean it shouldn't be constantly at 100% for a game 10 years old,
for example when I play Baldur's Gate3 it's around 80%

Is this a common thing, or am I missing something?