Upgraded net speed hoping for improvement....

[Vahlnir]

Called my ISP after making the first post on it here as well, they say there shouldn't be any issues between me and them and claim the problem is at SE's end.

That's how ISPs roll. It's always someone else's problem to fix. lol But anyway, I would look into your personal hardware. Something could need replacing, tightening or cleaning. SE has also acknowledged that the influx of players has caused some issues on their end, and they have been working to address it ahead of Endwalker's launch. I haven't had many issues myself, but that's not to say it doesn't exist. I would just try to rule out anything you can on your end. Literally everything, down to the last piece of hardware you're using, whether it's a console or PC. It could be a simpler fix than you think. I've been there, done that and I about kicked myself when I figured my issues out.