Their offense is pitiful. Sanchez played terribly, gifted Denver 7 points, and allowed them to hang around the game.
The Tebow mystique will vanish when he comes against a team with a decent defense and an above average QB who can hang 20+ on the board like it's nothing. Barring huge improvement, he will never be able to trade punches with quarterbacks like Brady, Roethlisberger, Rivers, Brees, and Rodgers, which is ultimately what you need to do to last as a starter in the NFL.
I think people are getting a little too caught up in the short term results without looking at the long term prognosis. Tebow has done just enough to squeak by a handful of poor opponents who didn't show up. Sooner or later someone will give him another real challenge (like in Detroit) and he will be exposed. That 47% completion percentage will catch up with him eventually.