I disagree simply because almost major website has significant usability issues with mobile. Often relating to touch input. I'm genuinely surprised anytime an image gallery is swipeable and it even half works.
It's easy to say that obviously they are shitty designers and/or coders and all they have to do is take the time to do it right. Well doing it right takes too much effort. And doing it right still doesn't get you all the way there. For any site with even a moderate degree of complexity there are always little bugs. It's just a fact of life in the HTML/CSS world.