I was really excited for Torchwood's future, after Children of Earth and RTD announcing he was leaving Who. I thought it'd become "legit", finally becoming worthy in its own right, rather than a Who supplement. Seems like CoE was the only time that happened. :/
I think a massive part of the problem with Miracle Day was due to how it was structured and written. It was written by committee, with 5 writers plus RTD and Julie Gardner deciding the overall plot, and then people called dibs on what episodes they wanted to do based on what most interested them. It was a shit idea, and makes the whole thing feel weirdly disconnected.
With Doctor Who, everybody except Gatiss and Moffat would get told what their episode is in simple terms. Fires of Pompeii had the description of "Pompeii, Fire Monsters, Soothsayers, Moral Dilemma, strong dramatic material for Catherine, to prove she's not just a comedian" - and that was what Moran worked with. Moffat uses the same structure, though like RTD accepted pitches off him, accepted them off people like Gaiman. Here, writers just did whatever they wanted within the rough confines of the overall series and it was all over the place.
RTD basically recruited a bunch of his heroes, including Jane Espenson, who did Buffy, which he loves. Never meet your heroes, as her episodes are arguably the worst of the bunch. Such a shame. Miracle Day has a really, really strong idea behind it, too, but the execution fucks it.
EDIT: Exterminieren - I think Big Pharma was a theme worth exploring, just without the earth vagina bullshit. The final plot twist was pretty ace, though, and I do like that character.