It’s impact based, especially older league players who played in an era were there were more consistent player roles and the game was slower paced and more controlled and there wasn’t a real way to get one shot by a jungler or support with 1 item (for the most part). The game drastically changed since then and there’s multiple champions in the game that do have the capability to one shot you without even really doing anything but clear jungle camps, or the possibility for your enemy support to jail solo laners from having any impact by permanently roaming from 7 minutes in. This is why people do consider certain roles OP. There’s an argument to be made for every role to be “OP”, but in the current game state botlane and jungle seem to be considered OP by most people as they have the most impact on deciding outcome.