The way I see it is, Kumble got a lot more opportunities to bowl overall due to being fitter and so available for selection and having less overall bowling support, which is part of why he has a large volume of wickets compared to Jadeja (as well as being a really good bowler). Jadeja for his part hasn't had the same number of opportunities, due to injuries and the selection group having a different view on how to pick players when Ashwin and more recently the pace bowlers also are available. That he's gotten more chances now is to his credit, even if it doesn't show in the bowling department away from home as for now overall.
Like a reason bowlers are picked is down to conditions, and you can't tell me that a lot of the games India have played away from home during Jadeja(/Ashwin)'s careers have had conditions suitable for spin all that often. Kumble if he played now would also be struggling with getting to play games away from home for exactly this reason, that the conditions don't suit him as much and that India can afford to leave him out unlike in the past. None of this seems to even exist though in some people's minds when it comes to rating players though, and I really wonder if they do watch and understand cricket as much as they seem to believe.
Like a reason bowlers are picked is down to conditions, and you can't tell me that a lot of the games India have played away from home during Jadeja(/Ashwin)'s careers have had conditions suitable for spin all that often. Kumble if he played now would also be struggling with getting to play games away from home for exactly this reason, that the conditions don't suit him as much and that India can afford to leave him out unlike in the past. None of this seems to even exist though in some people's minds when it comes to rating players though, and I really wonder if they do watch and understand cricket as much as they seem to believe.