There was really nothing that excited me about the return of Doctor Who for the Christmas special; generally they are only so-so episodes, and too often they overplay the seasonal aspect and throw lots of glitter-like aspects into the mix (by which I mean stuff that looks nice from a distance but is a mess and an annoyance when you get to it – source, I have a small daughter and lots of things with glitter stuck to them, and over everything else). On top of that the promotional poster looked cheap and silly – much like the superhero costume itself; and the title (The Return of Doctor Mysterio) screamed of cheese. So, like Doctor Who generally, I almost come at it now with a much lower bar for what will work for me – ie if it is not awful, then it must be one of the good episodes.
And by that yardstick, this Christmas special was quite enjoyable. It featured a topical (if overdone) genre of superheroes, had some sinister creature elements, showed restraint in a lot of areas, and generally was interesting in what it did with the characters. Generally it was greeted by those around me in the same way – satisfied indifference, which I do think is sometimes what this show is happy with – particularly in these big seasonal event shows. However this is not to say that the special is a good watch, because it isn't, and there is a lot to be irritated by. It wastes the aliens – it has some sinister images and ideas but doesn't follow them up, and the invasion plot really has limited menace. It does have a nice romantic plot but it doesn't do it that well, it is very much BBC sitcom level (and that is not a good thing). I liked the restraint it showed regarding the seasonal stuff, and that Matt Lucas was not a big part of it and was really limited in his impact (enough to be a good addition, not enough to be too annoying).
In the end it is an okay Christmas special but suffers from the same issue that much of Doctor Who – it really doesn't know what it wants to do, and feels produced by committee. The mix of content doesn't always work, and as usual we end with the Doctor being all dark and alone – something Capaldi can work with, but is never really fleshed out as it should be. In the context of Christmas Day though, it did work well enough to pass muster thanks to the state of the audience, and the low expectations/requirements the vast majority will have brought with them.