In the last 30 years, only eight teams have won a title. Seven teams combined for 29/30 of those. The same teams are winning over and over and over. So examining the last ten years is meaningless when that is what's happening, you'll get a false sense of parity by seeing it shared among six teams in ten years (as though six different teams win every decade).
The bottom 15 to 20 teams in the NBA can never, and will never win a title under any circumstances. There is zero competitive parity. In 30 years, only one team has won a solo stand-out title, and that's the Dallas Mavericks.
One other problem with this article, they say that U.S. sports gambling has been estimated at $800 billion (it hasn't), and then they link to an article that doesn't say that at all. That number doesn't even come close to passing a common-sense test. The link is referring to world-wide sports gambling.