What about the new Catalina operating system for my Mac mini. Should I upgrade or wait a while?

You can find out for yourself: Upgrading macOS without fear - Apple Community. Otherwise you will never upgrade.

There are still people complaining about Mojave; the same complaints as High Sierra, Sierra, El Cap, Yosemite, Mavericks...

Shall I go on?

Mountain Lion, Lion, Snow Leopard...

But wait, there's more!

Leopard, Tiger...

You might as well upgrade to Catalina, because whatever supersedes it is certain to be "the worst upgrade ever."

It also depends upon your model Mini and how much old 32 bit software you own. Eventually you will have to upgrade (unless you are 100 years old with a Mini you bought last year that will last another decade or so) but I think the conservative users are being late adapters and waiting a month or two to let all the early switchers work out the issues first.

Better check with adobe first. While the OS has been 64-bit for over 13 years, both adobe and Microsoft have only recently updated their software

Do you need any of the features added to Catalina?

Do you have any 32-bit apps that you cannot replace?

I’ve been running it a 2012 Mini with Custom Fusion drive and it works fine for me.

You better check with Adobe and your other app developers to see if they have a 64 bit version of the apps.