Connect the printer via USB and see if ImageCapture sees the scanner.
If not, download the IJ Scanner for Catalina software from Canon. Catalina was Apple's first 64 bit only operating system, which Monterey is too.
If not, try the Airprint driver which is picked by holding the Option key when adding the printer to the Printers and Scanners in Apple menu -> System Preferences. It can help to program the printer to have the same WiFi network settings as the computer.
When neither Image Capture nor Airprint works, VueScan is a possibility, as well as SANE.
Lastly if you have space on your hard drive, of at least 100 GB, you can use Disk Utility to format 60 GB or more to install the original OS that came with the Mac, using HFS Extended GUID formatting. Then run command-option-shift-R recovery to install the original OS that came with the Mac, and then upgrade back to Mojave.
Mail should have worked properly in High Sierra and Mojave, as all you need are either IMAP or exchange settings to use Mail. The presets for Yahoo, Verizon, AOL, Gmail and iCloud may be obsolete, but each of these work on IMAP.
Safari tends to get obsolete quickly. Many better browsers are on this tip:
Browsers by Mac operating system - Apple Community
If you still have a clone from the older operating system, and have not upgraded your Music and Photos library to Monterey, you may want to try these alternatives on the clone to see if you can go back to your older operating system by cloning it back.