Who the heck would want a FF lens that only goes to f/5.6 at 105mm?Not me, but people that want a light, cheap lens for landscape, travel, & studio use where shallow DOF is never used. 6D shooters would likely be the target for this lens.
Your logic makes about as much sense as saying who would want a crop sensor, or would want a camera any less tough than the 1D X.
There's this little thing called market segmentation. It's how big companies make money. Reference Canon's profits on the Rebel line vs. the 1D line.
I think the logic is ok. You are talking about what people will accept, not what they want.
I'm thinking about how dSLR's continue losing ground, and that putting out mediocre lenses which will produce disappointing results for new buyers accelerates that.
I'm committed to Canon. I'm satisfied with my gear, in some cases extremely pleased. I'd recommend Canon. Their CPS is fantastic.
But I do think it is ok to point out blunders and express disappointment.