Look, there's nothing overly wrong here. I want to get that out of the way from the start.
I've stuck with this show through some very grim periods of its thirty-three year run (yes, you read that right - thirty-three) and this episode certainly is not as bad as some others.
However, stacked up against what has been a very consistent series thirty-three it doesn't quite compare.
There are some nice ideas, but we've either seen them done better before, or they aren't overly engaging.
If this episode had been a part of say series eleven then it would get a massively higher score from me, because that was a middling year at best, but compared like for like it's not as good.