He has been though, for a winger in probably the world's greatest attacking team (when you consider quality of opponent) to manage just a handful of goals and assists in his first half a season is plain bad- especially since almost all of these came in games we were comfortably winning anyway.
Sterling or Mahrez would be crucified if they were offering such disappointing returns. In fact until mid-November Sterling had been offering similar returns and nobody was arguing that he wasn't playing awfully.
I don't know why every time someone points out that Grealish has started really badly here, it gets interpreted as them saying he was a waste of money and will never be good enough and needs to be sold. I'm only saying that so far he's been very disappointing.