The unpack process is usually single threaded, and a stock 5820k is slower than a ryzen 1600 in that case, so you're probably just running out of CPU performance. My server runs a 6700k and it's pretty slow to unpack even with nvme arrays

Excluding everything that is more difficult to deal with (like getting an SSD/more RAM/more swap on Linux), have you tried using different extraction apps? Peazip is good: https://peazip.github.io/

Edit: Here are some benchmarks for fastest extraction, Peazip is very good https://peazip.github.io/peazip-compression-benchmark.html#7-zip_vs_winrar

Your drive speed might be the limiting factor here, not your processor.

tf are you getting 4k torrents that are ziped and why??

If you're using the *arr apps to download, consider using unpackerr because it'll handle extraction and cleanup in the background.

What type of speed is your hard drive?

Some players can play rar files directly. Also look into rar2fs. I just try to avoid rars if possible