I think the reason some people have trouble with his performances is that he doesn't fit the mold of any 'great' player, his tool set is so vast.
His strengths are that he has a killer long pass and cross, and is a decent finisher (imagine how many more goals he'd have if half of those post shots went in, and nobody would be debating his contribution). His game is mostly reliant on being a stat padder, he wants to assist or score, in this sense it would seem the role of CAM or SS is ideal for him.
He isn't like Silva or Iniesta wherein he can dominate the midfield with agility and close controlled passing, and nor is he a midfield tank like Tottenham's pairing (Wanyama and Dembele). So he is in an awkward spot, the free 8 role is fine but when Silva is the more advanced 8, he has to stay back and that hinders him a little.
Honestly not sure what the best solution is, either Silva should be the deeper 8, or when we finally got proper fullbacks who can keep the width he can play as a wide inverted attacking midfielder, or he continues his development as the more withdrawn 8. A possible solution is going 4-2-2-2 and giving him the wide role, in this formation the wide attacking midfielders have freedom to drift inwards and become the playmaker, although I wouldn't sacrifice Pep's plan/formation for just one player.