slow mojave

I suggest you use the program created by Etresoft, a frequent contributor.  It will provide a snapshot of your system which we can analyze to possibly determine the cause of your problem. Please use copy and paste as screen shots can be hard to read. On the screen with Options, please open Options and check the bottom 2 boxes before running. Click “Share Report” button in the toolbar, select “Copy to Clipboard” and then paste into a reply. This will show what is running on your computer. No personal information is shown.

https://itunes.apple.com/us/app/etrecheck/id1423715984?mt=12

I see two issues: 1 - uninstall the Avast anti-virus software. It's totally not needed and will only compromise system and application performance; Do a search for the developer's instructions for uninstalling. When done rerun Etrecheck and verify that all of the Avast components are gone; 2 - Time Machine is not enabled. Do you have a current backup of your internal hard drive? If not that should be job 1. Operating without a backup is like driving without seat belts. You're fine until you need them.

And did you user this method to copy and past the report:

The report as posted has a lot of white space that shouldn't be there.

The I/O usage might be Spotlight indexing the drive. Open Activity Monitor and check to see which apps are using the most CPU and memory. Spotlight processes start with "md".

i don't see any of the usual suspects in the report

See this user tip:

How to use the Add Text Feature When Posting Large Amounts of Text, i.e. an Etrecheck Report… - Apple Community

Uninstall Avast. It is a worthless piece of junk which only causes problems on the Mac.