Catching up
Perhaps the best reason for making Tennant a new incarnation was that it acknowledged the passing of time for both the Doctor and Donna. Neither Tennant nor Tate were playing exactly the same characters that we had last seen in 2010, and it was important to address that.
Exploring how much time had passed for both characters is one of the highlights of this trilogy. The Star Beast allowed us to catch up with Donna and find out what her life had become. We got to see her relationship with her daughter Rose, and even her mother Sylvia had mellowed since we had last seen her.
But it’s in Wild Blue Yonder that we were given the best character exploration, especially for the Doctor. During the episode’s quieter moments, we got to find out how much the events of recent years had taken their toll on him. The emotional impact of both the Timeless Child and the Flux was finally addressed, adding so much more weight to some of the biggest moments of the Thirteenth Doctor’s era.
In fact, the Doctor’s ongoing trauma feels like the key arc of the specials, and indeed of the Fourteenth Doctor. The Toymaker revealing to Donna exactly what had happened to companions like Amy, Clara, and Bill (but not Rory, sadly) is a reminder of exactly how much the Doctor has gone through, especially since the end of Russell T Davies’s previous era as showrunner.