Steam's "Early Acces" is about giving you early acces to a game to see it in developement, until it's 100% done, for your early support to the developers. And for your money you should get a product with all the features they promised.
Steam's "Early Acces" isn't about buying a half-made game and be happy after that anyway, no matter if the devs abondon it or cut out important features they advertised.
"On Steam, developers make their own decisions about promotion, features, pricing and publication. However, Steam does require honesty from developers in the marketing of their games." - Chris_D - Valve Employee
Many of us bought extra copies of this game cuz the devs advertised it with a co-op function arriving soon and we all got scammed.
They arrogantly refuse to settle the situation and ban people from the Community Hub who complain about it.
Valve, please protect your customers!