It's a very refreshing approach to realistic movie-making by Bollywood. The cast and performances are undoubtedly great. A spy movie simply means keeping some ends loose for the imagination, this one did just that. However, the storytelling was a bit confusing for me as time to time it was jiggling among plots and subplots. It would have been better to show from the viewpoint of a storyteller, which in this case was Tabu initially.
OK, now the cons. The movie is too long. some parts could have been easily omitted like the scene where Robin gets a call from the doctor or the scene where he kills the spies in the shop. There are many. Initially, I felt like the director was trying to make a webseries and by mistake landed on a movie.
Overall it's great for 1 time watch. But It has many things of becoming a great one.