Most cricket teams rest their key players after the World Cup, and I think rest is necessary for some time. If you look at the cricket schedule of all the teams, their schedule is quite busy, due to which they often get less opportunity to rest. India doesn't have a dearth of good players, as the talent in India has emerged right from the time the IPL started being held in India.
Yes they play very well and work hard and struggle in all matches. Yes you are right because they work hard in all the matches due to which they get very tired.
Yes, because one match schedule ends, another schedule comes out due to which they cannot get rest.Yes, Virat Kholi, RK Rahul, Rohit Sharma, there are players who have made India proud.