(Not SquareEnix support, just attempting to be helpful...)

FWIW, I know a lot of people in my FC (or the allied Discord we share with a second FC for easy group content) who've been having this crash; switching back to using the old launcher seems to work fine to launch the game properly. Go to the 'Settings' button in the launcher, and you can swap to using the old launcher in the options there. Change the setting, quit the launcher, restart the launcher, and try logging in again.

So far, every one of my FC members who's had an issue launching the game has had that work to get them online, so hopefully it might for you as well.