First, I want to say that I appreciate this perspective and it is a valuable take.
BUT - I don’t think the game discourages the group aspect. Objectively, the game allows group/community events to come together quite easily, either you can choose to socialize organically or through their multiplayer grouping systems. They even encourage group activities in recent open world events if DF was any indicator, with no LFG required.
I think the player-base interacts with one another in a way that FEELS anti-community. Classic has a different set of rules and expectations for respect and camaraderie that Retail doesn’t hold anymore. Buffing others on the road, manually putting groups together through chat, randomly helping others in quests, etc.
Honestly, there’s little time to even type to other players in retail. Even in casual TW, I am constantly moving. The game itself has a different goal, so players act accordingly. Many people are in retail for the end, not the journey. Sometimes that can make others feel isolated and left out. For me, I just take the time to find others that seem to be taking it easy and /wave, buff, or offer help to those in need.
Be the change you want to see. Start a guild. Level with a newbie with no achievement points that you randomly find, make conversation, and be helpful if you can. Newbies are the people that get excited when a boss falls for the first time, when they get a new piece of gear, the awe of a new zone. Sometimes the shine wears off after all these years for people that have been around the block once or twice, or a hundred times.
Or, as you mentioned, do those things in Classic where it is a little easier. Same kinda situation, just a different set of expectations and older version of the game.
It’s tough, but recentering your perspective to realize the game is just that… a game. It is only as good of a community as the individuals in it that play. When I feel worn down, I pick an old achievement to work on. Right now, I’m doing the Tiller quests and achieves for Dog!
Best of luck to you, OP! Hope you find what you are looking for out there.