I understand that those who had planned to take days of work for this are upset, they have every right to be upset.
I also understand that this was a difficult decision to make for Yoshi.p, which is why I think it was something they had to do.

My guess is that whatever they really needed to delay it for was something that can be fixed within 2 weeks, but would create an even bigger shitstorm then delaying the release for 2 weeks have created.
A simple cost vs cost, does releasing it in this state cost SE more then the delay? At the end of the dey SE is a business and money is what ultimately drives decision making. Good thing for us that they have understood that a good relationship with the customers = more money.

And I know that Stormblood had a really bad release, well the entire expansion was rather crap, almost made me quit for good.
But there is a major difference between then and now, FFXIV is bigger and has more eyes on it, Shadowbringer is viewed as one of the greatest mmorpg expansions. That changes this to a moment where failure is not an option, either the articles and videos about Endwalker will hail it as the greates mmorpg expansion to date, or they will talk about how it is the worst failure in mmorpg history. Binary I know but that is what the internet has changed every conversation into, utter garbage or a masterpiece with nothing inbetween.

And again, I think that those that are upset have every right to be upset.