Yep, I agree with all of that. Holgate did better last year than I thought he was capable of, I thought he did really well, but only in a relative sense. I think he's a decent player who just isn't ever going to be good enough to be a regular starter for a side with any real ambition. As you say, he's young enough to prove me wrong, but from what I've seen he's just lacking a few too many things. I think people overrate him because he's usually more mobile than whoever he replaces in the backline and so instantly looks better in that regard. Personally i've never really liked the attitude he projects (whether that's his real personality or not I have no idea) but I know others have liked it previously and I think it's a bit unfair to have a go at him for now when thats what he's always been like.
Last season he did well, but again (a bit like I've mentioned about Gordon) he did well in a terrible team. I mean in a lot of ways that shows character and should be applauded, but shining in a terrible team doesn't always mean you automatically become good enough to play well for a great team. Pickford is probably a good example of this as well. Brilliant at Sunderland, where he was facing 8-10 shots every games. He'd let a couple in, save 6 ot 7, the team was shambolic and everyone would be like "chirst this goalkeeper is our best player, what a find he is". Again fine, but whats he like when he has nothing to do for 96 minutes and then has to tip one over the bar and he tips it back into play?
On the age thing I'm a bit conflicted too. I mean defenders can keep getting better post 24. I think of the likes of Jagielka, and Lescott who really improved a lot, and to a degree Keane has. But Jagielka and Lescott had a team built around their strengths and could do the basics much better than Holgate. This might sound odd, but I don't think he thinks like a centre half. I played centre half in my youth "career" and I was constantly aware of what was behind me. It's strange I still do it now is every day life (much to my partners annoyance), you kind of learn to protect your space when people are behind/next to you. He doesn't have that instinct. For that goal the other night, he watches the ball and he's got no idea what the man is doing. He needs to be more side on and so he can at least be aware of Maja. You take your position partially based upon what the striker is doing. Keane for all his faults is very good at this. He's also a lot bigger than Holgate (which won't change).
A bit like Gomez, when it looks good, it will look great, but there is always that "mistake" in him.
There's a wider story here about how we probably build people up a bit much, so when they are knocked down it gets harder to take. I don't think it's laziness, nor do I think the Nyarko or Schneiderlin comparisons are fair. Whatever one thinks of his attitude, there is a technical glitch in his game. He's an ok centre back and if he stays as 3/4th choice, I am happy enough with that. He has improved a lot from 18-24 and deserves credit for that. But he won't even get to a John Stones level, never mind beyond that. If he's our biggest problem in the squad, that's not the worst problem to have.