Sharding isn’t what killed the social aspect of the game.
What killed the social aspect of the game was systems like LFR, which formed a raid group for you by just pressing a button and waiting in queue, without needing to check in trade chat or get a guild. Then you were teleported to the instance, so you had ‘raiders’ who might not even know where the instance portal is.
Then you had cross-realm zones, which further deteriorated the communities. All those things OP talked about in his post? Those aren’t from sharding, but from the fact that there are no distinct servers any more.
All sharding does is help manage the server strain.