|Apparently he tried to watch Arc Of Infinity in one sitting|
Season 21, however, is too good an example of one problem to let it pass without comment. You see, the structure of the season is absolute crap.
We dealt with the season opener, Warriors Of The Deep, in depth last Friday but the quick version is this: it brings back monsters no one would remember, forgets what made them interesting to start with and had to be made with a massive cut in production time due to a general election. The middle of the season features three stories in which at least one main cast member enters or leaves and then is capped off by the infamously cheap and abysmal The Twin Dilemma that rebrands the Doctor as a physically abusive, selfish coward.
Structure is not the strong point of JNT's years in charge. It should be said in his defence that his first season had a good opener and finale but since it began with a bold new look and ended in Tom Baker's regeneration I don't know how much we can credit the production team with actually thinking about it so much as circumstances conspiring to make those stories memorable. Even in Season 18, though, we have the E-Space Trilogy whose middle story was an unused script from the Hinchcliffe/Holmes era that had sod all to do with the overarching theme.
Season finales seem to be the worst affected with duds like Time-Flight and The Ultimate Foe, low-key fare like The King's Demons and even Revelation Of The Daleks which looks like an event story on spec but gives the Doctor and Peri practically nothing to do and resolves almost without their involvement in the main plot.