As CMYK Profiles go, that is not a 'bad' Profile. OK it don't look like the perfect pretty picture. But that's why you profile the device. One challenge of CMYK profiling for Inkjet is getting the right balance of C to M to Y. For me M benefits from being highest, C lower and Y, the lowest.
On the Cannon, my personal challenge is getting past the fact the black doesn't get blacker when other inks are added. It makes for a shadow that is Black only, at the extreme end and can actually raise up when the other inks are added to it.
Trying to get a 'close to neutral' (a & b being as close as possible) is beneficial. When doing this the L value is going to go WAY up, but don't worry, Black is there to get that Low L* back.
In your Profile, you could try lowering Magenta a little.
For me, it's all about the relationship of the CMY inks and getting an Ink Limit that serves you best; Low L* but not so low that you loose shadow detail.
With CMYK, you get a lot more control, but it's a lot more work. Dialing in the Channel Limits, Balancing CMK, (you are even afforded the option of Gray Balancing CMY from the Highlight to Shadow, making your Printer perfectly neutral, before adding black. This should be BW Printing Heaven, i.e., G7.
To work those shadows out though, you have to start with limiting and balancing the individual channels. As an example, look at your Red Green and Blue, it they are too dark and heavy, bring the corresponding channels down a bit.
Just some thought.
Theory and Practice don't always go hand-in-hand, and this is one of those times.
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