Doctor Who really is at its best with four-parters. The story has enough time to breathe without becoming boring or slow. The Aztecs shows this well.

The sets and costumes are gorgeous, and there was clearly great care taken to make things accurate to life and history. The various headwear are especially impressive.

I like how enthusiastic Barbara is to be there, getting to flaunt even more of her knowledge as a history teach after Marco Polo, though it does veer into "white saviour" territory at times. I appreciate that it's balanced by the Doctor's insistence that nothing be changed and that the Aztecs are entitled to their way of life.

The various subplots are very fun. I wasn't super enthused about the Doctor's romantic interest at first, but the relationship grew on me over time. They are very sweet together. I like Ian showing up the strongest warrior with cunning. Susan gets sidelined a little, but what moments she has are good.

I think some aspects of the story could have been handled better, and I really doubt a story like this would have been attempted in today's political climate, but what we have is still really good and I'm happy it exists.