People seem to forget that he's only just turned 22 in October. That he only started 4 matches last year for Real Madrid, of the 21 he played in (please tell me what 21 year old has been a regular starter at Real Madrid in the last 5 years? Isco kind of with his 21-22 season). That he's only started 6 matches for us, in all competitions. That he has only played about 750 total minutes for us, which is just over 8 full matches. In which he has scored 5 goals and assisted 2 others. His pass completion percentage is around 80%. All told. A goal every 150 minutes, a couple assists, good passing percentage, good chance creation. If he calms down a bit and doesn't play so frantically, and starts to finish better he could be excellent.
Has he been amazing? No. Has he been decent? Yes. Does he still have a good amount of time to show that he can live up to his potential? Yes. Clearly.
I'm withholding judgment until at least the end of this season, if not waiting to see how he starts his second season with us, when he hopefully doesn't miss several weeks right away due to injury. People also forget that he missed part of preseason and the start of the season with injury. Let's wait to judge whether he is a flop until he's at least finished a season, and been given at least semi-regular starts.