At one hand I do understand new players struggling about being unable to play relevant content without additional paying (skip potions). On the other, due to focus on the story it's guite hard to change in its core.

What they can do is remove chains MSQ-Raid as they did with Crystal Tower sidestory not so long ago. So, let's say, as soon as you reach 60, you are able to start Alexander quests by default. Theoretically they also can unlock all dungeons by default, but it will be a mechanic thing: opening dungeon is an activity locked by quest (most of them are locked in side quests anyway, though). But there is another problem: raids and dungeons will be locked in areas... which are unavalaible for you because you didn't reach there by MSQ. So reworking all of this can take some time for sure.

Making parts of MSQ optional in the first place looks quite complicated. FF14 has a solid story, so starting right from 5.0 can be very confusing. It's like missing multiplication table and starting right from theory of limits. Still could be a good thing for those who is okay with this or for those, who level their alts, but then they gonna lose money for skip potions which, I suspect, is not an option.