The question I ask is, who determines the skill cap for the MSQ?
Let's get down to the nitty gritty. FFXIV's MSQ does already have a difficulty curve. You cannot say Sastasha is the same difficulty as The Keeper of the Lake, to give an extreme example. You can start comparing to other endgame dungeons, Baelsar's Wall, Ghimlyt Dark, Pagalth'an, The Dead Ends or any other dungeon you want really. While there might be some anomalies, the general trend is that the difficulty rises, it might not be by much, but it does.
With this said, there has been someone who has already posted in this topic saying that, due to personal restrictions, they struggle to get past certain bosses. I believe this person has also said they do not want it to be any harder (correct me if I am wrong), however, what about the person that cannot get to that point? They aren't skilled enough to get past that certain solo duty, even on very easy that they have been walled off from the rest of the MSQ. Should they not have a say in the difficulty of the game? If they wanted to make the game easier so that they could access the rest of the story, should that be allowed? Even if it means removing all complexity from a dungeon? Yes, it is an extreme point, but if the claim is that the MSQ should be accessible to virtually everyone, then that is the road you need to consider.
I don't remember which topic this next point was from, however I remember reading somewhere that someone could not complete a duty with trusts, so resorted to using the DF to get through. The healer can always res you if you fail and it isn't an instant wipe after all. The thing is, have they bothered to learn the fight or are they just expecting to waltz right on through? Is it fair to get carried through that fight just because you didn't learn from your past mistakes? This is obviously purely a mechanic problem, since DPS doesn't matter in dungeons (except rare cases of very very easy checks). If it is a case that their personal attributes doesn't allow them to clear, should it be made easier to allow them to clear it via trusts?
As with everything, there is a balancing act that needs to be achieved and you are not going to balance it to everyone's tastes. The difficulty curve needs to keep rising, even if it is a very shallow incline but at some point, you are going to leave someone behind.