I agree he played all the games safe, I believe he said (or implied it) himself in one of the press conferences. I also agree that they should play the classical until somebody wins. As Carlsen said in the post final press conference Caruana has the same right to claim he's the best in the world in classical format.
I would argue he played ALL the games safe knowing he's a huge favorite in rapid and blitz.
I would much rather they have to keep playing "classical" chess until somebody wins/loses.
That means that the players would be far more motivated to drive home an advantageous situation when it arises.
Carlsen's dominance in blitz is probably why he doesn't seem to be squeezing endgames into victories anymore.