This thread was started by someone going through the story for the first time. Once is enough for the issues to appear. Some people just don't enjoy the low level content, or would like to play with friends. The MSQ can make that unnecessarily difficult.
When it comes to alts, it doesn't matter if they're optional, the whole game is. FF14 provides the option to play alts and because of that alt character playthroughs are just as legitimate as single character playthroughs. Alts can serve practical purposes anyway as they let you optimize gear, RP, or interact with friends that you can't play with on your main (DC shuffle, etc).
Just remember that what is or isn't reasonable is a personal thing. While you might not see a need for alts or any reason to deal with the MSQ more than once, that doesn't mean that no reasons exist.You don't have to go through the msq over and over again every time you try out a new combat class. If you had to then fine I would see the point in changing it a lot because I can see how it could be tiresome to do it every time you play a new class. But this isn't the case.
I guess this is a difference of opinion, but I think asking for relaxed MSQ requirements is a minor change since it only changes the single player experience and only if the player chooses to take advantage of the change. If the change actually was disruptive or would make FF14 into something other than it was now I wouldn't support it because I don't want to alienate the current playerbase.All this fuss over something you only need to do once. It really puts into perspective how entitled people are when they demand to change the game in a huge way so that it becomes optional.
The story being replayable in Shadowbringers would also mesh well with this as it would let SE keep all of those things entwined with the story while letting the players that jump right into content still be able to play through the story when they feel like they're up for it. I feel like replayable story should be standard for a story based game. It's kind of off that FF14 went without this ability for so long.