I see 3 scenarios:
1) the new player is in for the story, in which case, a skip is of course not recommended, and they should be in for the journey. Maybe we should all stop saying it's a 300h story, and advertise it more as 6*50h games. Many people have been discovering franchises like Kingdom Hearts on the late, and had to go through all of them sequentially as well.
2) the new player is in for the endgame : buy a skip. It exists for a reason. The MSQ is and has always been something the dev team has been proud of, and they will always want people to at least try to experience it.
3) the new player is interested by both the story and the end-game: end-game doesn't start at level 90. It starts at 50. If anything, I think the solution should not be to encourage story skips, but to incentivize veteran players to run synced old end-game content. That's part of what the Mentor roulette is trying (but failing) to do.

Also, bonus 4) PvP starts at level 30 and is not depending on your level/MSQ progression. Make PvP better.
And, bonus 5) We don't know if the Criterion dungeons are lv90 content or if they have a syncing system similar to Bozja/PoTD etc. Maybe it could be a good way to give a taste of end-game content to new players.

I agree that they should make end-game content more accessible to new players. But I don't think it should be done by skipping any part of the MSQ.
I just think some of the optional content should not be completely locked behind the MSQ.