When I buy a carryon I make sure I buy one that fits a size and can go wheels-first into most bins. I put my backpack below the seat in front of me. I rarely have problems fitting my roller bag into an overhead since I get to board in zone 1, but I also try not to be “that person” and ruin it for the rest of the people.
Although my actual ethics class didn’t really use this method, I use the “If everyone did this would it be good or bad” method of ethics. If everyone who brought a carryon brought a 23″ carryon and had to stow it sideways we woul have much less storage space. I bring a backpack that fits under the seat in front of me so unless I’m in a bulkhead it goes under the seat in front of me.