I don't think you can make Ashwin/Sharjeel a Jonty regardless of how much you train. Fielding is also a talent. Some guys are born with strong lateral vision, sharp reflexes. They are able to quickly judge the power and trajectory of the shot played by the batsman. It helps them to get quickly into catching position/making a good save. Great fielders like Jonty, Symonds, Gibbs, Jadeja etc were always gun fielders. I have never seen a bad fielder turning into a great one. However, i have seen average batsman turning into great ones.
It will take a long time for subcontinent sides to achieve parity with the white teams in terms of fielding standards.
The white teams produce better fielders on average because they are better athletes and enjoy fielding. Most of them grow up playing different, highly physical sporting activities.
They grow up playing rugby, football etc. and are excellent swimmers as well.
Desi players mostly stick to cricket and even in cricket, they devote very little time to fielding and are focused on batting or bowling.
In street cricket in Pakistan, which is basically the breeding ground of all cricketers in the country, it is quite common for players to refuse to field if the captain does not give them a chance in batting or bowling.
This is the type of mentality and culture that eventually leads to a generation of players who feel like fielding is a burden.
India’s current struggles aside, they have done quite well in terms of bridging the gap because they have produced some very good fielding sides in the last 10-15. It seems like they have a developed a culture where the players enjoy fielding and recognize its importance.
However, it will take more time before they can weed out players like Ashwin, Kedhar Jhadav etc. who would be doing 9 to 5 office jobs if they weren’t good at bowling and batting.
Pakistan though is still stuck in the 90’s. Even then we had some great fielders like Ijaz, Afridi and Nazir but most others were liabilities. Today is no different - you won’t find more than 2-3 genuinely good fielders - good by international standards.
Steve Rixon made them work like mules for a couple of years and you could see the improvement, but once he left, the players seem to be back in their comfort-zone and cannot be bothered.
And I hate this attitude of players smiling when they drop a catch and then act as if they have lost their fingers. It is very common among the poor fielders in Pakistan.