I would love to know where you get your information from...
The Filthy is still loved by all of the athletes, and even more so loved by the people who have ridden them. The thing is, the ON3P athletes are either riding the Prester cause they're hitting big jumps and want a stable ski that carves super hard or the Kartel 98 cause they want the versatility of the wider platform in the park. The Filthy, being in the middle does get quite lost sometimes, but that doesn't make it any less fun, if ON3P said to all of their park atheltes "you all have to ride the Filthy in the park this season" (which they would never say...unlike some companies) not a single athlete would be upset by that because the Filthy is still a premier park ski. You have to remember before the Prester and the Kartel 98, the Filthy was the ON3P park ski, there really wasn't another option, so all the riders were on them. Once those two skis came around (mostly because of the demand of the riders), they split between the two (or just split their time between the two based on what they're doing that day). Case in point, I love my Filthy's, they were my go to ski for 4 years, but once I got on the Prester, I found myself riding them so much more, then the spring slush came and I wanted the more surfy and powerful Kartel 98 to ride in the park. It just comes down to preference, and when you can choose to have both the Kartel 98 and Prester in your quiver, and pick which one you want to use when, it makes the Filthy less desirable for them. That being said, if you want a ski that's between the Kartel 98 and the Prester (which is honestly most park riders out there - the Prester is a high performance race car and the Kartel 98 is a wider all-mountain park ski) then the Filthy is the choice.