Caruana had 12 chances to beat Magnus and couldn't.
I personally would have preferred if Carlsen had made a few more moves to see if Caruana blundered, as he had much less time and an uncomfortable, inferior position, but Carlsen had the right to offer draw. He knew he had better chances to win in rapid. If you don't like that Carlsen took advantage of the format to increase his chances to win, then the real issue here is the format, which had too few games.
In few words: don't blame Carlsen, blame the format.
The World Championship should NOT be decided by several time controls, because, if that's the case, then for the next World Blitz and Rapid Championships, we'll throw in a few classical 4 hour + games.