I think part of that is just our perception/expectation as fans. It happens a lot with academy players too. They come in for a game or 2 and you think they're acquitting themselves pretty well all things considered, but the more you see of them the more you start to realise what they're lacking, and the leeway you were giving them to start with starts to fade as you expect them to function like a proper first teamer. Holgate is error prone in my opinion, and the longer he plays for the more errors you notice.