These people don't understand
Kei is a groundstroker with a real shaky offense. Most of his points come from counter punching and being steady enough to make the opponent make mistakes. Guys like that Federer has awesome success with
Look at Andy Murray. Federer used to eat him alive, because all he did was counterpunching and groundstrokes. Until Murray added an offensive arsenal is when he started to beat Federer regularly, and be on sort of an equal footing
Same with Djokovic, he is a counter puncher AND an offensive game
Until Kei adds an offensive arsenal, and a better serve, he won't be a threat IMO