I'm on the fence with this one, but I'll have to side more with OP. This is mainly because people need to learn to ski on shitty setups first. It really helps you become a good skier. Especially to the point above how some good park skiers can't ski the rest of the mountain. I don't want to start a shitstorm here, so like I said NOT ALL park skiers, but some. Learn to ride the rest of the mountain properly and you can do it. People managed to do it on pencils back in the day, so 90 underfoot shouldn't be impossible. I did it for quite some time before I got pontoons. That being said, powder skis might just be the best invention ever, because skiing on pencils is a fucking workout, and although you can do it, nothing lets you slay all day like something 110 or more underfoot.
Sparknotes: Learn to ski the rest of the mountain and yeah you can use your skinny skis for pow, but damn is it nice to have something that floats!