Well, yes, you're right. That was a too sweeping generalization (I tried to make a point but overshot).
The missing qualifier is "when fully and completely implemented in the software" - and that's not always the case. Dual monitor support is a case in point, even Firefox doesn't do that. It can't convert source data to two different monitor profiles at the same time, so it uses the same profile on both.
Another case in point is the fact that you have to manually enable mode 1 in FF. It should be the default. And the other browsers should pick up on this, why they don't I have no clue. It's not as if there's any "risk" involved.
But when I say CM theory is complex I really mean the math and level of coding involved, which as I understand can be daunting (but luckily the engineers do all that for me). Functionally, the basic principles are very simple and straightforward, and once you realize that most of the practical considerations logically fall into place all by themselves.
I think much of the perceived problem is all the people who keep repeating how difficult it is. I don't know why they do that. This is the main reason I rarely go to the Photoshop forum these days - with every little CM-related problem a bunch of regulars pop up with the usual "This is too difficult to explain, there's no way in h*ll you'll ever understand, so just take my word for it". How helpful is that? On a BS scale that scores pretty high. Trying to inject some common sense into it only makes it worse. It's magic, and only the high priests understand. BS.
The point I was trying to make, without being entirely successful, is this: CM gets blamed for problems caused by lack of CM. The world is an unfair place.