Right, and that is why a lot of people are concerned. On the one hand, great that Canon is being less conservative with their product development, on the other hand offering video modes which may not be available if you shoot stills a lot (which probably represents a decent size of the community here and the target community for Canon), is just plain "out of character" for Canon...The 1ds3 wasn’t as hopeless as it’s sporty brother 1d3, I’ll give you that one, I bought one of the VERY first in my country and it was a nightmare.
it was a good write up from the engineers at Canon about the EF 85 f1.4 L IS, loads of people said this and that, and they answered everything.
time is one thing, the price point another. And a few hundred other factors.
since the 1d3 the only other thing I can recall was that light leak they fixed with tape,pretty much smooth sailing since that.
Faced with that, lots of people want to try and figure out whether they can fix it. I don't think all of it is malicious intent at Canon, I think lots of people here just like to try and solve problems.
There is no doubt in my mind Canon did a lot of design iterations, testing, changing. And yes, the constraints would be a long list, but doesnt mean they take all into consideration. Ultimately they thought they had the trade-offs at an acceptable position - and bar the cool down time & shooting stills then video, they have.
I think it is tough for Canon right now - how do they get insight into how much of this is genuine, how much is internet clickbaiting / growing your subscribers, much more difficult for Canon. We may all go ignore the YT crowd, it is just noise, but they're influencing potential buyers. Difficult for Canon to find what are the realistic issues being faced.
If mine arrives and I experience issues with video having taken stills, then I do intend to contact them. It's ok for people to vent here, but unless you have a massive following, then for us mere mortals contacting Canon is the best solution.
Re 1Ds III - I have 2 of them, but long after they launched, and all the fixes were in place. No doubt that experience influenced future designs a lot.