Yes, you can go and install various different apps which give you access to various different communities on the PC, there is no overlap or intercommunication between those applications or communities though. There is also no unified accounts which pass between any of these online networks afaik.
I am not talking about cross play. I am referring to access to games. Majority of PC gamers have access to the same libraries. Unless.. like i stated before you are gaming on another OS like Apple which is restricted. Thats why to me PC gaming is important. Anyone can own a PC and majority has the same access to the same games. Do you see PC fans fighting over games like the console fans do?
Having access brings gamers togother, today's gaming is far from this. Gamers are missing out on Gems unless they can afford multiplatforms, and ill admit i wasnt a rich child, i had to sacrifice my choices to play what i liked hence why i was a major Nintendo gamer in my youth.