He did good. He cast Peter Davison, who brought us a human, more fallible portrayal of our hero, and he cast Beryl Reid as a space marine (a lot of people think it negative, but trust me, BERYL REID in SPACE, what's not to love?) and he modernised the series, bringing back love and affection, after a period of decrease in popularity. He brought in Nyssa. He was responsible for the Five Doctors. He made the series fresh and yet...
He did bad. He cast Colin Baker. He created Adric (he only cast Waterhouse, because he had a crush on the fresh-faced BBC clerk boy who had a deluded desire to be as good as Olivier by the age of 20, instead becoming as good as a one-legged seal is at sprinting) and his ham-fisted tactics led the Great Michael Grade (a man who knows his entertainment, nephew of Sir Lew, a master of screen SF commissioning, and maker of rather good BBC 4 documentaries) to try to cancel it. Every spotty fan (including me) wanted to kill him at one point, as we thought as bad as Who was, surely it could get better. There was also the stunt castings, Time and The Rani, Doctor in Distresss, the escalating cheapness, the switch to all-video (which made it look like a kids show) and allowing Eric Saward near a scriptwriter. He created the Colin Baker look (popularised by Robin Williams in the film Toys, honestly Williams even said it himself, apparently) and the question marks, even criticised by Lord Barry Letts. He made characters different nationalities as gimmicks to attract foreign countries, which kind of worked with Tegan, as Janet Fielding really was an Aussie, but when your Pasadena-Californian Peri is actually from Guildford, eh...
Unbelievably Oscarwinning composing genius Hans Zimmer was involved, yes THAT Hans Zimmer!
When Sylvester McCoy was cast, oh no... And then it did, with stories like Ghost Light and Greatest Show in the Galaxy, and characters like Ace, who although likeable enough was failed, but an honourable failure, because she looked about 25, as Sophie Aldred was, when playing her, spoke too posh and too stupid (ie don't use your name as an exclamation! George!) yet we came to like her because she was easy on the eye and she convinced us, because we felt a bit sorry for her. RTD must've been scribbling notes.
But as good as JN-T could be, he wasn't as successful as the brilliance of Letts or Hinchcliffe. He didn't have a stable script editor-producer relationship, plus really he was wrong for the series. He was a camp figure, an openly gay man with a relationship with his production manager, Gary Downie. They lived in Brighton together! Downie wrote the Doctor Who Cookbook! He was a Brummie whose real name was Jonathan Turner, became double-barrelled to avoid a mistaken identity and had a style more suited to variety, or maybe a soap opera. Doctor Who is neither. Doctor Who needs good actors, not big stars and style, not colour.
But then again, it is a trap people fall into regularly. Especially when you mix chain, lady blouse and Colin Baker coat.
JN-T never worked on TV again, apart from setting Who-related questions for Mastermind and interviews, where he came across as a big teddy bear coloured pink. He turned down Bergerac.
He was a great man, though, rather odd, but he let the series continue, and when the series died, he was left holding it, as no one else wanted it or him...
All without mentioning a certain red-haired actress and her Pease Pottage-born character?