Plenty of what you mention is true and is a major problem with Twitter. That said, there remain some vibrant, niche Twitter communities where discussions do take place (the NBA comes to mind immediately)
Minor League Baseball as well. Speculation about scouting reports, and potential call-ups is really fun. I'm a huge baseball fan (as I imagine many here might be), and this kind of thing is just not talked about on SportsCenter and it adds a human element to The Game. Concur about the NBA. NBA-Twitter is awesome.