Speaking of things that bug me! The MMORPG descriptors of striker, tank, etc (and their variation) making their way into D&D.* I have no issue with describing common roles that emerge in game play, but when the roles become prescriptive instead of descriptive and playing the game without certain roles appears "impossible" instead of "how can I use what is available to me in different ways to overcome this challenge?" it strikes me as limiting, esp. to newer players who adopt that framework.
*at least that is how I remember it. It could be these roles pre-date stuff like WoW, but I never heard them until after - and certainly MMORPGs helped spread that nomenclature.