There is a biological age at which you cannot react fast enough. Kappa is way beyond that age to get his mechanics down.
I play osu! and I started at the age of 18. I am getting better at the game but kids the age of 15 are getting better much faster than I ever could. So basically I am just losing ranks at this point because younger kids learn and get better much faster than me. I am 21 now and I can confidently say that my slow progress is 50% due to starting (and playing) at a much older age compared to the rest and the other 50% comes from the fact that I just don't have the competitive drive anymore. It is a very mechanics-heavy game with little to no use of the brain. Just your aim and rhythm sense matter. This is a perfect example to use to associate the link between age and mechanics.
When 21 is already considered to be an old age to develop mechanics it doesn't matter shit if Kappa grinds 12 hours a day at the age of 30. He is not special and cannot defy the laws of nature. The people you are calling the "best players of the nation" are Amaterasu and Rite2Ace in VLT, who themselves are around 30. or other 27-year + pro players in EG.
Yes, he has the experience, a LOOTTT of experience. Plays much better on LAN compared to online but his mechanics are bounded by the laws of science.
From what we can see already, it does not take more than 6 months to become an experienced player in valorant. There are numerous examples. Jingg, Zekken, Surf, Alfajer and so many more are extremely young players and star players. Even without that 10+ years of experience, they are easily much better than Kappa.
He is old and should acknowledge that. It would be much better for the Indian scene if he moved on and became a coach for a team with a lot of young talent. However, unfortunately, he is in the playing 5 of the best SA team that does not achieve shit outside and all these resources could have gone into getting new talent into the scene.