First of all, I would like to say that we had a very good WC. Yes, we did not reach the final and ended up 3rd but according to me, we are better than most teams (we couldn't see how we fared against NZ but the NZ on current form would still be a 50-50 for us). Currently Australia, NZ and India are neck to neck at the top of world ODI rankings (I mean not the official ICC rankings; this is according to actual strength of the teams). India have a few flaws which can be easily fixed and if done correctly, can definitely improve their standing a lot more.
1. Jadeja - the only reason why he was persisted with is because of his experience and it was too early to throw Axar into the ring during this tournament. Now that its over, Jadeja has to go. Axar is an option, but I would either look for a spinner who gets more turn with the ball or look for a medium pace allrounder (thereby looking for another specialist spinner). Ashwin with that super successful WC has nailed his spot for quite sometime now as India's lead spinner. He needs another specialist spinner to support him in the middle overs.
2. Lower order batting - This can be tied to the above point, but India need to find some lower order hitter so that Dhoni (if he continues for sometime) can find a lot more freedom to go for the accelerator sooner. If we had one more lower order hitter after Jadeja, maybe Dhoni would have started playing more shots in the semifinal against Australia. He wanted to stay in the game for longer, and in the process the asking rate got up to him. It was essentially a checkmate situation that Australia put him in, and he didn't have answers. I wish one of the Pathan brothers makes a big comeback and help us beef up our lower order batting. Preferably Irfan because he is a specialist seamer. And good thing is, he is now a CSK guy which means he could hopefully get more support from Dhoni.
I think the other areas look fine. We saw how Yadav responded when he was persisted with. Yes, he continues to be wayward but with consistent backing, the guy can really crank it up. I am waiting to see Aaron make a strong comeback to the side at some point in the future. These fast bowlers can be wayward, but with more games under their belt and more fine tuning, they can improve the line/length and combine it with their natural raw pace. India's big success this tournament was their bowlers (Yadav, Shami, Mohit and Ashwin). The continuance of fine tuning is what needs to be done.