Fans think he's shite because quite frankly we haven't had a player like that in our midfield since Masch, perhaps even Didi.
Can is an enforcer with huge potential, people forget the guy's not even 24 yet. Every time you watch him, he does something that you just know will translate into a huge strength in the future, be it long balls, passes in the box, tackles etc. Compare him to someone his age like maybe Kevin Stewart, and you'll see what I mean, for his age Can is an exceptional PL midfielder that will only get better. You're just not used to having someone with balls in the team, someone that will take every opportunity to commit dirty fouls, then bitch about it to the ref and get away with it, then run with the ball across half the field without anyone of the opponents able to give chase.
We simply didn't have a midfielder like that in a long while, mainly because our last two managers simply didn't see physicality as strength. It is actually quite painful watching teams like the two Manchester clubs and Arsenal, where they take every opportunity to complain to the ref and use every dirty tactic in the book to get their way, we simply stopped doing that at one point, and it shows in our results against weak opposition, that's why Can is such a welcoming addition, his attitude is similar to that of Ander Herrera, except Can's better at football.
Stop underrating him, he'll be class and deserves that contract extension.