There are normal dungeons, heroic dungeons and mythic 0s before you get into keystones. From a design perspective, someone going into a +2 should already know how to play their class as well as the layout of the dungeon. The only way Blizzard could stop players from skipping over the intended progression levels are by putting some kind of requirement that would require you to do every dungeon at every level before moving on, which would be terrible for the players that do know how to play.
I mean, duh? That’s not a design flaw that’s just playing with better players.
I have no issues in 2s on my alts. But I generally also join or invite players that have a main IO score.