I have a new 2019 iMac with 8Gb of memory and a HDD (not an SSD). Yes it's the lowest-end 8Gb iMac from last year.

With no apps running, nothing in the apps to start on login, with a new virgin account created yesterday, with the latest MacOS installed, opening system preferences - just opening it - can take over 30 seconds. Every time. With a beachball wait cursor.

This is not just a little slow. This is unbelievably slow. This is slower than my 10 year old MacBook Pro.

I've run every test on it that I can think of. Checked for processes that are using CPU. Checked for free memory. 

Does anyone have a clue? 

Could it be misconfigured somehow that makes it truly unusable?