How do I switch back to Catalina from Monterey?

If you have a last Time Machine backup from Catalina, and no subsequent operating system's Time Machine has written to it, then you can boot into Recovery mode and select Restore from that Time Machine backup. That will wipe the current drive, and reinstall the Catalina operating system, your home directory, and settings just as they were prior to the upgrade.

If a subsequent operating system's Time Machine has written to that Time Machine drive, you cannot go back to Catalina without losing all of your personal data and home directory. I do not recommend switching if this is the circumstance with your Time Machine drive, or if you have not cloned the Catalina drive prior to the upgrade.

Am sure there are reasons but has one considered working through the issues presented in Monterey before switching back.

If one provides more details and issues presented, we may be able to assist.