While it sounds nice on paper people will move past these dungeons regardless of if they're still "Skill-based" or not. People leveling up will be more likely to not experience it with the cap [and I say this because over time, as game's mature, people are less likely to go back and do that kind of content again] than experiencing it without a cap [because someone might take the time to carry them].

You have to decide which way you want to err, but a modern game design standpoint would err on letting people experience the content; even if they don't contribute.