Within any fan base, their are certain people who overrate some players because of a personal fixation. While I personally thought Simmonds was overrated going into last season because of his defensive failings and mediocre skating, he improved on the former some in large part due to a pretty significant improvement in the later. Now, I generally think he is pretty fairly rated by most.
Couturier is probably somewhat overrated because he is still young and offensively inconsistent. While people love to point out his ES scoring and tough assignments, very often he gets a pass for his periods of poor shooting, infrequent, but bad mid-ice turnovers, and so-so skating. I understand why it happens because other fans annoyingly look at stats and dismiss the potential and offensive ability (if a little inconsistent) that those who watch a lot see. Fans are probably a little over protective given the overly harsh evaluation of Couturier's offense and often criminal under-rating of his defense, especially on the PK.
Couturier would get better with opportunity, but he would also need to improve his consistency of offensive play, particularly shooting accuracy, to take full advantage of any increase in opportunity. Yes, opportunity and consistency are probably linked in this case.