I'm not saying he's 'forgotten' how to dance! By out of practice I mean strength. Its not easy to regain the lost strength unless you've been working on it even if you don't dance. Trust me, I am talking out of experience. You can definitely do the steps easily but because you don't have the strength to keep your body under 100% control, the finess of the step doesn't come. Hence, the step doesn't look as amazing as it could have. It looks rather "dheela-dhaala" which is the case with Kapil.
Ok, let's say I accept that theory about dance, which indeed, I think is highly possible. You know dancing so you'd definitely have more spot on experience than me.
But what about the low profile? What about the non-existant Kapil in the show? Questions are asked to everyone, watch the new videos for this week, even Akshat and Abhishek and Sushant... Why only Kapil is non-existant?