Most of the episodes I find overrated I still like just not as much as other people, so it's faint criticism. But i'll have a go anyway

The Girl in the Fireplace: imo it only gets so much praise due to being the best of a weak season. The droids are creepy, but everything else seems fairly average to me. The acting is nothing special, the death letter isn't as emotionally stirring as they would've hoped, the droids plan makes no sense and I can't help but shake the feeling that The Doctor comes off as selfish trapping Mickey and Rose on the ship. It's still good, but nowhere near the level of other Moffat scripts