FCPX 10.4.10 on Catalina 10.5.7 extremly slow

Are you using Color Finale and Neat Video in your project? They are both slow in processing, especially Neat, which is very slow. Don't know about FilmConvertNitrate, but would suspect it.

How exactly have you tested for speed? Try it on a simple RED 8K in a 1080 timeline.

Make that all those plugins are updated to the latest versions.

Please run Etrecheck and post its full report here.

Use the “additional text” button and paste the report into the text box.

Please run a new Etrecheck and post the report here.

Cleanmymac claims another victim :-(

This hideous piece of **** has crippled so many macs...

You may want to start by uninstalling it, but ultimately you will probably need to do a clean install.

Ten minutes of RED 8K set to fit in a 1080 timeline took me 15:47 minutes to export to ProRes on 2019 MBP.

Unfortunately it is not nearly as simple.

To uninstall, you have to follow their instructions.

And to make matters (a lot) worse, uninstalling does not undo whatever damage this has already caused to your system.

I'd say be prepared to do a clean install, but if you are unconvinced (and you are not alone - so many times I've read the "oh, but I have had this for years and never caused a problem" phrase...), here is something simpler:

Install a fresh version of Catalina on a separate drive (preferably an SSD, as HD are so slow, but even an HD will do).

See how a clean system works.

The mac has made upgrading so easy over the times that many people upgrade continuously for years, system over system and onto different macs even. This has the propensity to accumulate stuff that after a while is not so compatible anymore.

So even if there is no problem, it is usually best to do a clean install, at least when upgrading to a new OS (like from Mojave to Catalina, for example). This gets rid of old stuff and keeps a nimble system working fine. Migrating user accounts is fine, so documents, photos, music, etc are all preserved. Just don't other stuff (applications, settings, other files...).