Never really thought about this before. At the time TNG was born, many were upset that the classic characters had no part in it. Now many people's introduction to Star Trek was seeing two or three series concurrently, each with different groups of people who barely ever mention each other. They accept it as given, but it's actually unusual. When I was introducing someone to Trek, this seemed hard for them to accept, with frequent questions like how Kirk and Spock fit into TNG, or where the Enterprise is in DS9. It's strange how we're now at a point where people would literally consider it "jumping the shark" to connect to a character who was the lead for almost half of the franchise's history.