Literally every popular MMO ever made has had first-day or first-week expansion server problems.

All of them.

It's not something you can prevent, because even with stress tests, you have no way of knowing how many people are going to go 'hey, this expansion drops tomorrow? let me buy it real quick.' You can get an idea with stress tests and player counts, but considering that you're not only managing people who left to wait for the next expansion, plus old players coming back, plus the usual playerbase, plus all the WoW players jumping ship, plus all the people seeing news about FFXIV's meteoric rise in popularity and wanting to try it out, plus streamer watchers wanting to play with the streamer...

After a certain point, the number of players becomes literally unknowable.

Square Enix is a business. They want to make money. If you really think they neglected their server capacity in the face of a tsunami of players, knowing the potential outrage, then either you're just wrong, or Square is not so dissimilar to Blizzard than I thought. But either way, an unknowable amount of incoming players is impossible to plan around without an infinite amount of servers.

At a certain point it goes beyond white-knighting and not white-knighting, and just people accepting the truth of the situation and people upset that they have no foresight.