AbdulAlhazred
Legend
Again though I am not telling people how they need to play, but doesn't it behoove us all to have an objective idea what the different forms of play are?It is however a core assumption of D&D. Other games work differently with different controls, costs, ways of balancing the different roles. It's comparing apples and oranges to compare D&D to PbtA games for example.
Those options may be preferred by you, they are not preferred by a lot of people. You don't get to decide for everyone else the best way, especially when it's worked for the most popular RPG for nearly half a century.
As for a core assumption of D&D, 2 decades ago I would have agreed with that statement, far less sure about it now. WotC made an edition where that's arguably only one option, and it's pretty much established only to a limited degree at most. 5e is supposed to be a big tent and clearly has elements like background benefits that are intended to belong to the players. So yeah, it is the most common interpretation, but far less so than 1980s classic D&D.