The 8 episode limit hurt this season...
A lot of people are catching on that there is something missing this season and that's the complexity in the doctor/companion relationship. I really think the 8 episode limit and Ncuti's other commitments hurt this season.
We've had amazing moments from Ruby this season, and I feel like I know her really well to be honest. Her personality, her likes, her dislikes, her hidden fears, her trauma's, how she handles herself, her hopeful nature etc... I also feel like I know Fifteen quite well as a character too. He's bouncy and joyful, he's very confident, ignoring the bad to focus on the good, but unfortunately maybe he does this too much and doesn't let himself see the darker sides as much... Which is why the ending of Dot and Bubble was such a shocking moment.
I think I know both of these characters quite well, but unfortunately I don't know them together. I don't know their relationship and that's because we barely see them together.
Ruby Road - They only meet halfway through the episode.
Devils Chord - Definitely a few moments between the two, but the threat of the Maestro is so larger than life that it doesn't give much room for the Doctor and Ruby to connect.
Boom - Ruby is pretty much dead for half the episode.
73 Yards - No Doctor
Dot and Bubble - They're both hardly in the episode and the ending is essentially all about the doctor (rightfully so but still).
Rogue - We haven't seen it yet but I could definitely imagine a similar issue as Devils Chord with Jonathan Groff's character.
The only episode this season that has focused on showcasing the Doctor and Ruby's relationship has been Space Babies. I think it actually does a great job at it, but it's the only one and it's not enough.
I think this season is a great collection of Doctor Who stories and it's done a great job at establishing who Fifteen and Ruby are as individuals, but it has not done a good job at establishing their connection. 8 episodes was definitely not enough and now that's becoming clear.
I also think the philosophy of giving us as many interesting doctor who stories as possible, although not a bad way to do things, didn't work out as well because of the shorter season. If we had 12 episodes we could have 8 crazy doctor who stories, but also have 4 more run of the mill stories that focus more on fleshing out the character dynamics, but with just 8 episodes there's just no space for that.