Ind has an archaic T20 strategy where they try to start slow in power play by keeping wickets and then accelerate later. Mostly only works when chasing moderate totals, but in all other instances (which is the majority of games), will fail. If you see the top 6 batsmen, almost all of them are captains of their respective teams in ipl and play anchor roles, so when they play for Ind, few of them have to change their natural role and play aggressive, and that doesn't come off well often. You don't see Jos butler and Jason Roy playing anchor roles in Eng domestic T20 and then try to switch to aggressive mode in internationals. A player like Joe Root can't make it into Eng T20 side, and see how Eng is doing in ODI/T20.
India needs an Eng like moment where they revamp the entire side with younger/T20 specialists. Despite IPL being great etc etc, if you see the top performers in this years IPL in same UAE pitches, none of them are even in the squad, forget about the playing XI. So selection based on reputation versus T20 specialists/form hurt Ind badly. No wonder they fail to make playoffs.