I think there is certainly an element to travel tourism that has soured a lot of people, but also the world has become a very cynical place to live in. Mass tourism machines like cruise ships have several layers of issues to them, but they are also the economic centers of many marine locations that wouldn't be what they are without them, but that's also sort of the problem with them.
Add into it the cheap air fares, etc... and it opened up the world to the average Joe, who has not the best manners or realistic expectations all the time.
Then, add in the fact there are too damn many of us on this planet that anywhere remotely interesting to visit is packed from dawn to dusk and it gets annoying having to wait for things all the time, especially at home for the 3 months or so people want to see your little stretch of the world.
I get it. I don't agree with it all but I get it. I work in tourism to a degree. We are spread too far, everywhere you go there is more of us.