I think it depends on what someone means by "genius". Waldners style of play simply isn't possible in the current stage of TT. At least not if you're aiming to be the best in the world. In my eyes Koki Niwa is a similar "genius" if you're comparing to the Waldner style of play. Then I think Niwa is the closest you'll get and is a pleasure to the eyes to watch.
But then again, FZD, Ma Long, Xu Xin are also geniuses in their own way.. and so is Harimoto.. I think we're all just looking at the word genius differently. If we just look at one of the definitions of the word: "an exceptionally intelligent person or one with exceptional skill in a particular area of activity."
How do any of the players mentioned above not fit this description? They're all geniuses in their own right. Waldner was absolutely exceptional at the time no doubt, with a unique, non chalant type of playstyle which made everyone fall in love. I don't think there's a player today that has such an elegant playstyle, but that's partly because the game doesn't really allow it. Niwa tries and does a good job, it makes you wonder what Niwa would be like if he was born in Waldners era.
Harimoto is exceptional as was Waldner and several other players. Waldner induced incredible feelings in people from his playstyle which is why I think many romanticize him, and rightfully so! I do think some people misunderstand Harimoto. All I see in this kid is a burning passion for the game, which he expresses on the court.. which unfortunately and understandably gets taken the wrong way. I can feel his passion and while I have mixed feelings about his choing I can't help but like and root for him as well as want the very best for him in TT.
It's very difficult to make these comparisons x player is a genius and y is not. They're walking different paths in different eras. It's unfair to compare Harimotos type of genius to Waldners.