People have been Kobe is declining for the past couple of seasons. He's still putting up elite numbers. The only legit regression is defense, and you could argue that at least part of that is more apathy or disinterest than anything. The struggles of the Lakers as a team gives Kobe critics reason to argue he's fallen off. But while you can question his leadership or his ability to build team chemistry with teammates, you can't really question his level of play. It's still near the top of the league. If he's declining, it's not that noticeable.
In the three head-to-head match-ups between Kobe and Harden this season:
Kobe: 30.3 PPG, 7.3 RPG, 6.7 APG, 3.0 SPG, 43.7 FG%, 25.0 3P%, 73.7 FT%
Harden: 22.0 PPG, 6.0 RPG, 7.3 APG, 0.7 SPG, 37.5 FG%, .267 3P%, 83.3 FT%
I realize that the Rockets won all three games. But it's not like Harden was destroying Kobe. If anything, the head-to-head match-up between the two make a stronger argument for Kobe. Like I said, it's still a debate as to who's better.