I bought the AMD 7900XT GPU last week and have been trying some different options here and there.
I did some research before buying it and saw good fps across all the games I wanted to play, I tried benchmarking the same games and easily got 80 fps lower than the original benchmark.
Temps are all good so it's not thermal throttling.
Using the Ryzen 7 3700x, 2x8 GB Corsair RAM
Your cpu is bottleneck your gpu and that's why. The cpu is too weak for use the card 100%, download msi afterburner and test with a new game like cyberpunk and if you have low fps and low gpu usage your cpu is too weak that's it. (i advise you to buy a Ryzen 9 5950X i think this will enough for the 100% usage)