I don't think thats the case, almost 3 years Kohli is captaining the test team and the results are pretty good. I will not judge his limited overs skills based on IPL as RCB is a screwed up club wrt player management.
Wake up and smell the coffee.
Kohli is probably the dumbest captain in IPL history.
He has had all the power, financial backing and support to build a good team and he still fails. Worse part is that when players leave RCB and go elsewhere, they start performing well.
He can play the tragic hero role year in and year out but slowly people are realizing it's not RCB, it's him.
How did Kohli the captain manage to do things which Dhoni himself could not do as a Test captain (winning a home series vs SA, winning a test series in SL and winning a home series vs England).
The Dhoni mafia (including his PR agency) has build this aura around Dhoni as if he is running the show in LOIs , fact is test results show India team prospers when the legend Dhoni gets booted out (or retires out of shame). Hopefully this will happen soon in LOIs
Simple.
ODIs and T20s are far more tactical than tests.
In tests, you need to make sure the specialists are picked, backed and you maintain energy in the field. Man management and culture matters more than tactics.
Kohli the test captain made sure he backed pacers. He doesn't allow bowlers or fielders to slack around in the field. His infectious enthusiasm rubs off on others and his aggression instills a feeling of belief in the players.
In that aspect, Kohli is a WONDERFUL test captain and I rate him.
It also helps that he got good and most importantly clutch test batsmen at his disposal and 2 spinners who were at the peak of their powers.
Tactics wise, Kohli isn't great in tests but it doesn't matter much as you have to set conventional fields for most part. Kohli's tactics work in tests as he focuses on the basics, keeps the energy of the team high and makes everyone believe they can do it. However the times when opposition goes on a complete offensive (Chandimal, Roston Chase, Aus piling on runs in the 1st test), Kohli starts panicking real bad and it affects his decision making and it makes everyone in the team super nervous.
Problem for Kohli in tests is that his team selection is atrocious. He is lucky that he had other players in the team to clean up after his mess (eg - Pujara in SL, Ashwin & Saha in WI). However SA away series selection was a fiasco one too many times for which we paid the price. I don't even want to go into his decision to decline BCCI's offer to fly the test specialists to SA earlier.
In LOIs, the situation is completely different. Tactics matters a lot where Kohli fails miserably. He knows he is crap and he needs Dhoni who takes over when situation goes awry. Moreover, his team selection is atrocious to say the least (but here I can't give hi the blame alone, there is Dhoni there too pulling the strings). There is no long term planning. The only good decision he took was getting the 2 wrist spinners in after the CT 2017 fiasco which is well and good, but it's not some groundbreaking move. The world had moved on to wrist spinners and it was just a matter of time for India to follow suit and test them. And don't even get me started on how easily he drops Kuldeep as opposed to Chahal.
All in all, Kohli has his positives and negatives. His style works for test cricket (leaving aside his selection fiascos and tiff with Kumble) but in LOIs, it's going to be a struggle.
Luckily for him, he has at his disposal, a highly talented and well rounded team.
Can Kohli improve/change? Yes, he can.
But this is my observation based upon his performance uptil now.
