Wish! They don't market GG or even MAX as an AAA game maker. Even Lee has mentioned in his developer vlog to go look elsewhere IE; the big titles like Unreal if you want AAA features. So, that's no problem. Multiplayer can be found in this Unreal stub;
Also look into the deeper documentation. Places like; https://docs.coregames.com/references/cameras_and_settings/
Anyhow, core has those crucial requested features ready to go NOW that GG lacks (3PMP). One thing that immediately strikes me in particular; take a look at the graphics and models style. I haven't seen the dank, grungy, drab, moldy style GG and MAX promotes. As it appears up to date in both FASHION and FUNCTIONALITY, it should fare quite wonderfully and help you make your game expeditiously. Also- scratch the $, they don't charge for it, but to the credit of GG, they do seem to be taking some hints from this engine as what direction to go with MAX, though I cannot verify that officially.