I have mixed feelings about the Pertwee Era.
On the one hand, I enjoyed Jon Pertwee as a Doctor, especially in season seven. In fact, season seven is one of my favorite seasons. As the new format of the Doctor’s Earth exile began, the Doctor became a reluctant scientific adviser to UNIT, working with the Brigadier and the intelligent and highly competent Liz Shaw. Season seven was a bit darker than what followed and was fairly diverse in its offerings. Seasons eight through eleven, however, were lighter and less serious. It isn’t that the show didn’t tackle thought-provoking material. Barry Letts (producer) and Terrance Dicks (script editor) always wanted the show to be about something in the real world. But the Brigadier was written less intelligent in subsequent seasons, and Jo Grant rarely rose above a bumbling-assistant caricature. (“The Green Death” is a notable exception.)
Even with these quibbles, I enjoyed the experimentation in this era: UNIT allowed for recurring regulars like Captain Yates and Sergeant Benton, the Doctor was given a Moriarty figure in The Master, and the Earth-bound stories allowed the show to make direct commentary on contemporary (1970s) England society and politics.