A lesson here for professional users whether it be MacOS or Windoze.
You were given the choice of upgrading or not
You were strongly recommended to take backups
You had the opportunity to research this forum and also the wider web to see what possible problems your mac might experience.
You could have taken a non-work day to test out Catalina and subsequent incremental updates and within hours work out if it was for you or not. i.e. keep or revert.
Apple make it easy for you to revert to the original OS, even publishing simple instructions and a free Time Machine program, the best backup app on the market.
https://support.apple.com/en-gb/guide/mac-help/mh15216/mac
I did all the above researching and testing, and apart from a problem with an old version of an app it went smoothly. IMO the fastest MacOS ever.
I worked for a London civil engineering company when they moved from Windoze 3.1 to Windoze95. It was a six month project to test and convert. Every single app (before the word was invented) had to be tested and signed off.
If you just pushed the “Install” button to get the latest Thing with no research, no preparation, no test plan and no backout plan then you will have to accept the “I can no longer work” situation with a red face.