Yeah, it's nice to romanticize the past, but it just doesn't hold up to facts. Between 1980 and 2000, 6 different teams won the NBA championship: Lakers (6), Bulls (6), Celtics (3), Rockets (2) and Spurs (1). Since 2001, 6 teams have also won the Championship: Lakers (4), Spurs (3), Heat (2), Celtics (1) and Mavericks (1). The idea that there is somehow less parity now than in the glory days of the league doesn't really add up. The last time there was any parity in terms of championship winners was the 1970s, and no one romanticizes that era of the NBA like they do the 80s-90s or the 60s (when the Celtics won everything always).
Frankly, I don't think we like parity in our sports (in general). It's so much easier to construct a narrative around the Lakers and Celtics because they have a long history. The Thunder and Heat? That's new to us. And then we have teams like the Grizzlies or the Warriors or the Clippers or the Nets who are historically bad, but now they're legitimate contenders while the old stalwarts falter. It throws off our narrative and our preconceived notions about who the good teams are. It makes it more interesting, sure, but it also requires more effort to keep up with who is actually good, and who has time for that?