You could argue that Lewis wrote the book in 1950 when he was 52 years old. He might have been conservative and sceptical about all those new trends and fads at that time. I just think that introducing those beliefs into a children's book in such a dishonest way lowers its value drasticly. That's what Pullman criticises: "The supernaturalism, the reactionary sneering, the misogyny, the racism, and the sheer dishonesty of his narrative method". I wouldn't go as far as that, but I see where he's coming from.
Yeah, Pullman sounds kinda grumpy sometimes but he's absolutely right about Narnia (although I partially disagree from him concerning The Lord of the Rings).
I read it kinda late, I was already a grown up with strong and firm opinions about religion, and I was already a fan of HDM.
I tried my best not to dislike it before I read it, but I also felt sick so many times, specially in "The Last Battle", that I don't think children should read it too young, not even christian kids, because even if you're christian doesn't mean you have to be so racist, ethnocentric, intolerant, sexist and also absolutist (yeah, Narnia has kings and kingdoms just like any other epic fantasy, but the difference is that in those other fantasies, that kingdom is not decided by God. It's plain anglicanism, which gives the terrible notion that political authority should always be obeyed and never questioned).
I try to judge the storytelling as something written in a time when children's book was not supposed to have adult fans. It's for kids only, so it's very soft and silly, totally unlike what we have today with HDM, Harry Potter, Percy Jackson, etc.
I don't criticise the books' religious subtext, because I defend the right of storytelling to be ideological. It's one of the greatest genius of His Dark Materials, and Pullman did it too, with the notorious difference that Pullman had an argument about sin and wisdom/innocence and experience. He gave us a reason for why the Republic of Heaven is the best option and why God had to die, while Lewis was just selling an idea and never gave us a reason why a world with Aslam is any better than a world without it.
So, Lewis was right to be ideological, but was wrong to just sell it, and to underestimate the rational thinking of his readers.
But the biggest problem is the christian messages per se, which is the worst from this religion. Some of those messages shouldn't be supported even by christian, but there's too much to be sick and angry about when you're a humanist like myself.