This really wasn't even worth responding to, but I find I couldn't resist. Building on what a few others have said already:
Last year in the regular season, KG...
finished 3rd in the MVP vote
was the Defensive Player of the year
Finished in the top-5 in the NBA in every advanced stat going (PER, Roland Rating, Wins Produced, etc. etc.)
Last year in the playoffs, KG...
led the Celtics in points and rebounds
was among the league leaders in every advanced playoff stat measured (PER, Roland Rating, +/-, etc.)
Held every PF he faced well under their season numbers 1-on-1 (including 3 very good players in Josh Smith, Rasheed Wallace and Lamar Odom), while simultaneously giving a lot of help to slow down the LeBrons and Kobes of the world.
Led the Celtics in 4th quarter scoring (obliterating the "only plays 3 quarters myth"). And no matter how close the games were, he still led the team in scoring. He led the Cs in 4th quarter scoring in games decided by 10 points or less, 7 points or less, or 4 points or less.
And all of that is just ON the court, not in any way touching on all of the intangibles and culture-changing impact that EVERYONE attributes to him. Many argue that his off-court impact was as big as any on-court impact, and ON the court he was huge.
If KG has fallen off, as the OP suggests, and STILL was able to do all of that on a championship team? I think the only word that works is...wow.