Ah, good grief. Finally solved my problem. Found the solution a ways down in a Microsoft forum thread.
Solution: (In Windows 10)
Right click on the Windows Start button, select Control Panel
Click on Devices and Printers
Single regular click on any of the printers listed (I clicked on Microsoft Print to PDF)
Near the top of the window, a bit in from the left, you'll see the text "Print server properites", click on that. (It's a ways right from Add A Device)
In the new window, select the Drivers tab
In the list "Installed printer drivers:" select any and all Canon MF... type names one by one and click on Remove one by one.
From there I took the option to "Remove driver and driver package" (who knows, maybe "Remove driver only." might have worked)
I believe the next window said something about having collected the drivers, and I clicked on the option Delete.
I did get an error message about "Failed to remove package cnxrpua6.inf. Access is denied". That's why I wrote above that maybe the "Remove driver only" option might work better. But the error didn't matter since I was instantly able to install the Canon drivers I had downloaded. No reboot required.