As expected, I had to figure this out on my own since I'm sure nobody even understands the problem. The newer MacBook was somehow garbling up the username/password in a way that none of my other devices were doing. Nothing that any forum, blog, or tech support page even hinted that this could be a problem, they were always of the mindset of "reboot" (yeah, really helpful).
Here is the solution:
1) I had to connect my newer MacBook to a working wifi hotspot (thankfully there was an "emergency" option in my area that has a 60 minute time limit)
2) Once connected to the Internet, I had to navigate Safari to the corporate-provided login page for that wifi hotspot, (not the login screen the MacBook automatically opens, and not the login screen that the hotspot opens, there is a huge difference between all of these)
3) Put in the username and password on THAT login screen, but DO NOT HIT "connect"
4) Switch your wifi connection to the hotspot you actually want to connect to, but while it's connecting you have to quickly hit the "connect" button on the corporate-provided login page. This bypasses the MacBook from ever pulling up a login page or sending out whatever stupid security protocols Apple has put in there to make it difficult for people to use a laptop as intended: a PORTABLE computer. Viola!, connected, even though the Safari webpage never gives me a "connected" status, the little progress wheel just keeps spinning. But, I'm using that connection right now to type all this out. Stupid, but it works.
Here's what I believe is happening: the username and password being sent out into wifi space from the corporate login page isn't garbled up like the MacBook tries to do through it's captive network process, it's basically bypassing all of that. Since the requested login info is already sending through the wifi card at the same time you're connecting to the wifi hotspot, the authentication process is happy, since it's just looking for those packets in the correct format.
I hope this helps somebody else having problems connecting to captive networks. It's incredible that Apple doesn't even recognize that this is a legit problem. Somebody messed up something in the wifi security process. Maybe have that checked out instead of focusing on making slicker desktop icons and social media apps?