**FIX FOUND*!
I was able to solve this problem. It came because I have a MSI GD65 Gaming MOBO with Qualcomm Atheros Killer Network Manager. Even though I swear I had ended the process and it still didn't work, I figured out how to fix it.
In the Applications tab of this program, find all GTA V and Social club entries, turn them from whatever they are (probably Highest (1)) to High (2).
Then under the Advance Tab, I turned Default applications settings to default priority (2- High).
I am unsure if both of those steps are necessary, or the order which I originally did them (may be grayed out if Global Application Control isn't Enabled)
Since I did this, I have been playing with my friends and randoms where before I couldn't join anyone at all.