How do I get rid of Catalina --- I lost use of Adobe and there was no warning about this.

Yes. I don't use TM myself, but I know the idea is to erase the drive (you have to in order to get an older OS installed), install the OS you want and merge in your backup.

Apple has instructions of how to restore a TM backup here:

Restore your Mac from a backup - Apple Support

Apple has been warning of major changes to the OS for 2 years. This kind of thing is why you don't upgrade your computer without first having a full, restorable backup.

Catalina isn't a "terrible" update. CS6 is ancient software with no more chance of being supported forever than any other software under any OS. Your choices are:

1. Restore the backup you made before installing Catalina.
2. If you don't have a backup, you'll have to erase the drive to go backwards. Back up all of your important data, first. Your emails, images and other documents. Then erase and install the previous OS, followed all of your third party software. Restore your personal data.
3. Replace CS6 with the CC Suite, or find alternatives. Adobe Photoshop Elements 2020 does much of what Photoshop does for a fraction of the cost. $99 for a one-time cost license. You will lose CMYK support with Elements.