It has not even been 3 years so calling it a few is inaccurate. You are acting like its not recent when 2014 is recent. He is still in his prime. Yes he took a bad injury in 2015 and like every other NFL player rushed back from it, but if you actually watch the games and watch what is going on Joe is actually playing pretty well. His accuracy is just better than it has been. Now a lot of those balls are not being converted to receptions like should but to paraphrase Gizelle he cannot throw it and catch it. If you put a ball into both hands of your receiver your job is done, if that ends up a catch, a drop, or even an INT as has happened multiple times to a rather worrying degree as long as you deliver the ball to the receivers hands especially getting him either in stride or protected from the hit you have done all you can do the rest is on the other guys.
That is at its core the nature of being a QB. A QB cannot MAKE you look good, but only give you the opportunity to make yourself look good. Some players are just not good enough to take advantage of it but most are. There are handful of WRs who need less help then others but they are not as important as a solid OLine because with protection and a solid QB the numbers will happen for anyone.