I remember how Halo 1 for PC (which I played a lot of back in the day) had multiple bandwidth presets for the online multiplayer. Basically, the setting you chose placed a cap on how many people could join your hosted sessions, with a maximum of 16 people if you chose the T1/LAN option. The dial-up (56k) option allowed for a maximum of just 2 people.

If an 18 year old game can't perform optimally online on dial-up, then no way in the seven hells is an MMO going to perform well.