Converse with fellow players
Someone came up with this solution on Reddit. I'm testing it out on my side to see if it works, but apparently a lot of people have said that their stuttering significantly dropped or even went away even in full lobbies.
EDIT: Finally, a decent temporary fix until an official solution comes. The issue isn't caused by Gameguard, though. Reddit OP is wrong, it's caused by something else since you wouldn't be able to launch the game otherwise.
It's working for me. Now I can stay at lobby