Because having to cite it implies there's some sort of aspect either holding him back from production he's never had or that he's actually bringing in wins with his usage, rather than that usage being a symptom and one of the very reasons why this team has been losing moreso than winning with him as the first line center.
In any case, do you feel top lines are actually being shut down against this team? In the case of low end top lines, I'd tend to agree: but who cares about that.
Really, if he's not suited for his current role, and he's not, then he's not "bringing wins". Then, it becomes a matter of determining whether he's suited as a #2 or a #3 on a "winning" team and where he ranks amongst those comparables. The problem here is the further you go down the lineup, the closer you come to what's an average regular roster player. Meaning the question then becomes how much better he is to that player and according to that, how valuable he really is.
For example, nobody would doubt how much better Kuznetsov is than that average 2nd/3rd line player - and that's why the Capitals were a legitimate threat i.e. they had players who "win".
The problem on this board though is the standard for players and forward rosters has become much too low, making this concept foreign to a significant part of it. Like, the argument has really become how not that bad these players are. I mean, let's push for better players and put these guys in better situations for the team.