And since I've seen the comparison between RTD and Moffat come up elsewhere (and this post gives me a reason to riff)......add to that the fact that he's also working on Sherlock...
Some have cited RTD's ability to run Who, Torchwood, and Sarah Jane as a comparison point for Moffat. "RTD did three shows simultaneously. Why can't Moffat do two?"
It's actually a false comparison.
RTD was a Rick Berman figure on Torchwood and Sarah Jane -- overseeing things, making sure the paperwork was signed and nothing was going over budget. He handed Torchwood off to Chris Chibnall, after polishing off a script that had been collecting dust in the drawer for a decade, and RTD didn't come back to Torchwood in a creative capacity until Children of Earth, which you see in The Writer's Tale fit into RTD's schedule while Doctor Who was on hiatus between "The Next Doctor" and "Planet of the Dead." Similarly with Sarah Jane; he cowrote the pilot and handed it off to others to run.
Moffat has his hands creatively in both Who and Sherlock, because he wants to have his hands in both. Yes, Moffat could hand the reins of Sherlock off to, say, Mark Gatiss, but why should he? More importantly, why would he want to?