He's not a "bad" center.
Bad penalties(lazy), poor defensive zone play, and barely 50% on faceoffs overall, and a low ozone faceoff win %.
Mostly though the poor defensive zone play.
I got off the "product of panarin" train earlier this year, when panarin was out, but now its more he's more of a passenger on a line and doesn't drive play very well for someone who wants to be a 2c. He's got a good RH shot, and he's not bad on the pp.
I think most people though just really dislike him because quinn loved him and he ended up blocking chytil.