In some cases, the original reasoning behind divisions in sports was to minimize team travel times. This was back in an era when travel was by bus or train, but seldom via air. Fans got used to the arrangement and probably expected it. Fans prove again and again that they tend to dislike changes.
Today, divisions serve little purpose other than to give fans multiple leaders, which makes more people more interested, perhaps selling more tickets. One team flying solo at the top of the standings can be a buzz kill. Think: baseball, circa 1964.
What the WNBA is doing seems to me a sort of virtual division setup. I like it.
As to some other sports playoff arrangements, NASCAR has alienated what is left of their original or old school fan base with their cockeyed "chase" format. Only this sport could concoct a scheme where one driver could win every race except the last one, finish second in that one, and still NOT win the season championship. What they wanted was "excitement." What they created was a rather randomized finish. But at least, with the present setup, they made it less likely that anyone can break the "sacred" seven championships won record of Earnhardt and Petty.
If the WNBA is guilty of anything here, it is the reverse. They have built a system in which the best teams have an easier path to the championship and the TV exposure, etcetera. It's a stacked deck to an extent, but most fans are probably good with it, as am I.