To be brutally honest, this is Leo dressed as Robert Redford dressed as Gatsby:
Redford's suit and collar cuts were off, but the colourings were spot on to what was described in the book, as I recall. In particular, Gatsby is described specifically in this ivory suit/silver grey shirt/ gold tie combo in a particular sequence in the book. It may be less a case of imitating the irritating Redford and more of a coincidence that they are similarly dressed as they both are based on the description in the book. [huh]
You're right and Redford did it better from what I can tell so far.
I loathed Redford's portrayal, myself. Horses for courses, I guess! I'm looking forward to seeing what young Leo does with it.