Well, of course Air Canada customers are cheap.
Humans are cheap. This is not news.
I think it's hard to talk about the issues in a general way, though.
Take seat selection. Before paying for seat selection was "a thing", people on one PNR generally got seated together. Now they don't. People didn't stop paying for seat selection, things just got worse.
Or how about Aeroplan rewards -- they promote getting what you want (see: "plan A" commercials), but reality is different. They're setting expectations that are unrealistic to begin with.
Change fees -- only seem to go in one direction, and are clearly out of proportion of the clerical costs of the change, almost to the point that the change fee substantially approaches the cost of the leg you're changing. Kinda hard to not be grumpy about it, especially when most changes are probably ALSO resulting in higher airfare on top of the change fee.
I could go on
Some passengers' grumbling is over the top, but there's a lot of blame to be spread around here...