Okay, just wanted to update you guys on how I fixed this: I bought a new router. I basically just plugged it in, configured an ID and password and everything works beautifully.
If you think about it, the internet isn't exactly exploding with people complaining of wifi problems - with 40 million preorders you'd think we'd be hearing far, far more people with this problem if it was just iOS 8 - So it's likely that we all share something simple in common: we all have old routers.
My old (D-Link 628) router hadn't had a significant firmware update since like early 2011.
Those old routers lose support so they can sell you the new routers that can connect to modern hardware. It's called "planned obsolescence," I believe. Maybe it's iOS 8's fault our routers are now obsolete, but it's hard to blame Apple for choosing more advanced technology as time marches on. I know, it *****.
I got the Netgear N900 and it's way faster than my old router, and at further distances. I got the bigger N900 because of all the devices my family owns, but if you only have one or two people in your house there are cheaper options. The Apple brand was $50 more and didn't do anything special compared to the other ones (according to online reviews).