I don't think there's anything wrong with your rendering time.
The problem comes from your hardware configuration to me.
It's pretty weak actually.
You can see that your memory is constantly full, so your computer swaps, which slows down the render.
That's why the processor load falls down to 8% when it waits for the images to be loaded.
Rendering time also depends on your HDD bandpass.
From USB, it's slow.
From SATA, it's better.
From SSD, it's really fast.
Neat Noise Remover is really the best option in terms of quality but it has a cost, it needs processing power.
Anyway, if you expect to do noise removing on 4K plates, with 8GB of ram, you're gonna have awful rendering times.
You should have at the very least 32GB, but 64 is recommanded.
In addition to that, Neat uses GPU acceleration, so the better is your graphic card, the faster it renders.