Yah... something is clearly wrong. Etrecheck should not require 36 minutes to run and the nominal I/O usage of 0.46 MB/s seems low. I suspect the hard drive component of your fusion drive has deteriorated, but it is possible you simply have system file corruption or that one of your install kernel extensions is causing problems.
Suggestions:
- Restart into safe mode. Still slow? (see: How to use safe mode on your Mac - Apple Support)
- Create a new user account. Restart and login to the new account. Still slow?
- Uninstall the Western Digital software. I've never heard anything good about it, but theoretically tests 1 or 2 should already check if this is the culprit.
If either 1 or 2 works normally then the problem is with something you have installed. If both are equally slow (or slower) then the problem is either system file corruption or a failing HDD. Erasing the fusion drive, reformatting, and reinstalling -might- work but I would suggest instead purchasing an external USB 3.0 SSD and reinstalling macOS onto that.
For using an external SSD as a boot drive see: Use an external SSD as your startup disk … - Apple Community
My one comment on the above guide is that basically any SSD large enough to hold your files will work. You don't have to limit yourself to the one 3rd party brand sold by the Apple Store although that is certainly a safe option.
