that's because people who primarily play role-playing video games tend to have a bias towards the games of their favorite developer, who generally tend to follow the same basic gameplay mechanics throughout their games. if someone else's idea of what an RPG is goes against their idea of what an RPG is they get really indignant and complain a lot.
for pretty much everybody else an RPG is mostly defined by character progression, which has been a feature of tons of games for over a decade. it's why JRPGs are still widely considered RPGs even though virtually every other thing about them - exploring, solving puzzles and interacting with different characters in order to progress a linear narrative - is a core staple of adventure games.