But the printer profiles should work, so yes that is a mystery. I use Epson though (printing with PS managing colors) and it’s straightforward - PS does the transform to my custom printer/media profile and the output on my 9800 is dead-on to my monitor - so I’m not going to be much help with the Canon driver, sorry.
You didn’t mention - have you tried soft-proofing with your printer profile in PS? How does that look? Look at your printer profile in ColorThink or ColorSync if you can and see if there’s anything wonky with it (spikes, weird shape) - might be something going on with it.