I'm not sure he's the worst, but he'd be really low down on my list of who I'd want to write another one.
Sadistro, you'll never convinve me he's a great writer, he may not be a terrible writer, and may in fact be better when he isn't writing sci-fi, but frankly it wasn't neccesarily the sci-fi elements that are terrible about The Silurian 2 parter, there's a terrible perception of time that's in fact so bad I thought it was intentional and part of the arc, there's characters that make little sense (one minute the Silurian scientist is Dr Mengele, the next he's everyone's cuddly uncle!). You mention Law and Order, but wasn't he adapating US scripts there? I'd need to check to see which episodes of LOM he wrote, but in all honesty that show isn't uniformly brilliant. And as for having someone to sense check his work, he has, both RTD and Moffat should have been doing that, that 42 was still so dull after that, and that the Silurian 2 parter was so poor speaks volumes.
As for what Cornell would or wouldn't do, you're right, we don't know, but I think if you were a huge fan, as RTD, Moffat and Cornell all are, you'd have to be really strict to limit yourself. And yes Moffat can be repetitive, in the same way RTD could, or Gareth Roberts can be, in the same way I think anyone who wrote lots of episodes of a series would be, but whilst familiarity can breed contempt, it can also provide comfort, and there are plenty of people who don't like the show any more because it feels different to how it was under RTD, in the same way plenty of people will not like the next show runner's version because it'll feel v different to Moffat's.
Cornell is a good writer, but I'm not sure he's had any production experience which is where RTD and Moffat had the edge, and as I say that's what I dind worrying about Chibnell. That said I'm not sure who I would want, and it might well be someone we've never heard of before, and they might actually do a better job that RTD or Moff...who knows?
You don't like Moffat's version of Who, fair enough, I think you just need to suck it up and live with it like those of us who weren't always enamoured of everything RTD's version of Who was, enjoy the stuff you like, try not to get too bent out of shape about the stuff you don't. And as for a hit show needing variery, Who was quite predicatble under RTD but people still tuned in in their droves, and they still do now with Moffat's version.
Showrunner's are a bit like actors playing the Doctor, if you're not a fan you don't have to worry because you at least know they won't stick around forever (well unless they're Tom or JNT

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