He is actually not perfectly suited for T20... T20 is for power-hitters because a 28(11) is much better than even 51(40). If India has power-hitters like in West Indies, then people like Kohli, Rohit, etc. should actually sit out of T20 (That's what even great Sachin did, and he realized that even in those days!) Nothing to feel ashamed of to admit this... These people value their wickets more than the runs they score, and this is essential for Test & ODI formats! You don't want these guys to completely change their game-style and get destroyed in other formats. (That's why WI team is so weak in tests and even ODIs) You can say about ABD, but ABD is a different player, he is somebody like Dhoni at his best! While Kohli is like Amla (superior to him anyhow, because of chasing ability). Actually Kohli is not the only target, even Dhoni & ABD are criticized for their T20 abilities at various times, because even they are best suited for ODIs.
But IPL has provision for all players because of dearth of talent because it is still a domestic tournament with restriction on quantity of international players (+ also it is for financial benefits to the players). Hence if these players play, and if they don't perform up to your expectation, then you can't blame them or call them selfish! Here you are talking about RCB, but let me tell you that there are similar such players or even worse ones distributed in other teams as well. But those teams also have the players who are specialists in T20 and hence these players get hidden behind them. So its a fairly distributed contest in that regard! Or in other words they get complemented & will play the supporting role (hold one end or something). Problem with RCB is they have lot of missing links... Kohli can play that anchor role, ABD can play the power game, but in between everyone else are missing... You need next set of power hitters which they don't have... (Also the bowling issues to make matters worse) If you look at successful WI T20 teams, they probably had only one anchor (Samuels) and rest all are power-hitters revolving around him. This will work for RCB and Indian team as well, with Kohli playing the role of Samuels In fact Kohli will be 10 times more effective than Samuels "provided" (please note) that he plays with a team similar to WI. But the problem is India has another guy in the same mode (for T20s) - Rohit. So the solution is - you should actually pick only one between Rohit & Kohli for T20 team (choice is yours & obvious) But Kohli & Shastri will think otherwise & mess up things! Sure they will form a very good team for ODI, but not for T20 and also they will do the same mistake for Test Matches.
It becomes very hard to balance and play according to all three formats... Kohli got tested in this, but since he is the best around he tries to manage it, but still things slip up sometimes... Similar thing happened to Rahul where he was somewhat tested for all three formats, but him still trying to cement place in the side it became too difficult to live up to the challenge! Dhawan also got affected and could not deliver at test level even though he wishes to do well there... In fact Dhawan would have been successful even in Tests if there was only ODI and no T20s around (he would have tightened his defense).
Hence the problem with RCB is the whole team, team composition, management and even captaincy! So you can criticize Kohli - the captain to some extent and not his batting in the tournament (In fact he has batted as well as Dinesh Karthik, Kane Williamson or other successful captains if you notice closely! It is about the team!) But you cannot remove him from captaincy because he is the captain of Indian Team itself! Things are complicated!