I'm going to be the controversial one here and say that I love Season 23 and say that it's one of my favourite Seasons/Series in Who. Colin is still as loveable playing the cocky hero and has a kinder heart, but not to the point of him being a different character. The production values may have taken a miss compared to past Seasons, but I actually like it's fast pace and explosive action (that carries over to the McCoy era). This is also the first Season where I adore the music (not saying that I didn't enjoy past Seasons music, especially in the 80s, but I just enjoy the compositions and instruments here more). And lastly, my most controversial opinion: The Valeyard is my favourite villain in the franchise and I prefer him being the polar opposite to the Doctor over The Master.
The Mysterious Planet is an underrated story. Whilst the stakes aren't presented as high as much as the story wants to, Robert Holmes still manages to add witty dialogue, and there's still a sense of adventure and fascinating worldbuilding. The location filming is blissful (although I'm biased to the Autumn setting), and the ideas are imaginative. The only thing that I don't buy is the 2 boys and their acting (which are better than the kids in the Twin Dilemma, but it's still not great).
Mindwarp gets a bad wrap, but I love it and it's one of my favourite Colin stories. The point of 6's characterisation is that the machine has made him completely insane, the point where he was during in his post-regeneration in Twin Dilemma, and he's trying to regain his mind back again. Perhaps it would have been nice to have a few more stories that showed how far he had come in terms of development (because he has definitely grown but there needed to be more). The outdoor sections of the planet are the most gorgeous locations (and I wished that many planets had as much vibrant sky colours in the Series). Brian Blessed is deliciously entertaining. Sil is just as great as in Vengeance on Varos, The Timelords are the most ominous and threatening they have been since The War Games and the last 5 minutes are the most brilliant and have the most dramatic performances in Who History, with Colin bringing his best performance.
Terror of the Vervoids is Pip and Jane's best script by a fucking country mile. The set design is lush and vivid, I like the moral quandary with the Doctor trying to reason with the Vervoids, but is then forced to murder them, Mel is a underrated companion and I enjoy her peppy attitude, there's a good murder mystery vibe that left me guessing who the culprit was the first time, as a murder mystery should and I enjoy the tone of it. The Trial scenes were definitely getting obtrusive by this point though.
The Ultimate Foe is a rather mixed bag. Part 1 is excellent. A wonderful gothic atmosphere, the Matrix is just as imaginative and surreal as it was in The Deadly Assasin, the twist with the Valeyard may be the most fascinating twist in all of Who, the wonderful direction makes scenes feel foreboding and menacing, the cliffhanger is gorgeously terrifying and Glitz adds great comedy. But Part 2 feels disappointing compared to the first part. The Master feels like an unnecessary addition to the story, the surreal nature is thrown off for science technobabble and the climax feels anticlimactic. But I still found the whole story entertaining for the most part.