I don't think Milner has ever been poor for us, and only turned out good now as some seem to portray it.
In his first season he got double digits in assists despite eventual criticisms (if I'm not mistaken he ended the season with something ridiculous like 15 assists). The season after that he bizarrely turned into a left back and was one of the best in the league. Last season he wasn't bad either.
Milner has always been a great player for any squad, but a player with some limitations, like anyone not called Lionel Messi is. He can't be expected to be the thinking man in a lethargic midfield with even more limited players such as Emre Can. If constantly pressed, Milner doesn't have the skills or burst of speed to make things happen in the middle of the pitch either. But in a more balanced side as we are this season, and not being pressed too much like last night (one of the reasons why Henderson also had one of his better games on the ball), he's excellent.
And defensively he has the intelligence and discipline to cover the right spots of the pitch, plus the fitness and the mentality to get stuck in and contribute enormously.
He's a flawed player like all others, and will be better in a system that takes the best out of him, again like every other player. I've always been a fan but he amazingly continues to impress me even after all those years. Even if he eventually loses his place in the starting XI, it's fantastic to have Milner in our squad.