I thought this was an excellent article. Then again, I've often wondered the same myself so maybe totally biased. Yes, costumes are harder to do on live action TV and make them work. But it has been done. The Flash TV series comes to mind (Complete with a reason for the suit) though even they seemed to balk at costumed superVILLAINS. It wasn't the costume that killed that show, it was the cost of the FX budget. Now that we can do more and do it cheaper, that excuse should be fading. Lois and Clark had a pretty successful run, even if it focused more on the romance than the super powers.
I think , considering the sheer number of people who have seen animated superhero material, superheroes on the big screen, and so on, the public is more willing to suspend disbelief and give costumes a chance than WB execs realize.
There just needs to be a good story with good acting involved.