I've been experimenting with the entire connection / disconnecting / internet connectivity issue, and I have to say, what I'm seeing is, well... insane.
Some context first: I work remotely so I've invested in a solid internet connection. At any time during my normal workday, I can have multiple chat programs, a persistent email app, literally dozens of internet pages, a 2nd computer on the internet, do online calls (slack, zoom, etc.), and stream either music or a movie in the background without issue. I use wifi for my laptop, but my desktop has a direct wired connection so that it's stable.
However, as soon as I try to connect to FFXIV, if I have anything more than just a couple internet pages open (aka most of what I just listed above), I get the 2002 error. I can't stream, can't have email open, effectively anything else internet related going on or even attempting to hit a data center results in a 2002.
If I get into the queue, I've found that I can then start streaming something, for a little while, but if I have to pause or select something new, aka something that takes up more bandwidth, it'll crash out the game with the 2002. And then if I try to reconnect quickly to hit the 1minute timer, it won't let me and will instead just keep hitting me with 2002 errors. And it won't stop with the errors until I reset/refresh my entire connection, by which point I'll have lost my spot in the queue.
However, for the last couple of nights I've had no issues, as long as I have absolutely nothing else connecting to the internet. I've been patiently waiting through 2-3hr+ queues (I've been playing later to try to accommodate, which has sucked on other levels), but no 2002 errors during login or while playing the game. Only thing connecting was FFXIV.
So, this all essentially tells me the following: The bandwidth requirement for SE's launcher to do the connect check is INSANELY SENSITIVE.
Probably one of, if not the worst, system I've ever seen in my 40+ years of life and working with technology. I'm actually legit impressed considering they're not some little indie company and an actual mega-corporation, lol
Welp, since I just lost my place in the queue after having wasted an hour, now I need to get back on track to my chores and maybe try again later today...
Edit: Adjusting some details above due to Catwho's thoughtful addition below