I think it's obvious that Moffat just doesn't like the Daleks and only ever included them for the sake of fan service - or contractual obligation if the Terry Nation Estate rumour is to be believed. He left their reintroduction in Series 5 to Mark Gatiss, even admitting that he didn't pay enough attention during Victory's production. After that, they were more or less reduced to cameos for the first two years, playing small parts in stories that could easily have worked without them. The two dedicated Dalek stories Moffat wrote himself portrayed them as weak, dim-witted, ineffectual, mindless drones unable to fend for themselves and controlled by their travel machines, the latter defeating the entire point of them being mutants in tanks rather than mere robots.
Another thing Moffat fucked up was their relationship to the Doctor. They wiped out his entire species, they're supposed to be the creatures he despises most in all the universe. How and when did he go from
this to castigating resistance fighters simply for being soldiers and appearing totally nonchalant about the existence of a new Dalek empire with mass prison camps?
At least RTD knew how to build them up as a credible threat before ruining everything with the inevitable deus ex machina. To give credit where it's due, Russell's enthusiasm for the Daleks also shines through in his dialogue. Even in a story as fundamentally flawed as Journey's End, there are real highlights like the Supreme Dalek's chilling questions about emotion after Donna's apparent death, whereas Moffat's Dalek dialogue is the most lazy and uninspired I've ever heard. You can almost hear Briggs straining desperately to inject some semblance of life into the insipid, generic, repetitive drivel he's been landed with.
From taking a backseat to James Corden pissing about in a shopping mall to becoming the remote-controlled playthings of Missy, the Cybermen fared no better. It's like he just couldn't resist taking the piss out of TruWho icons. The return of the Mondasian variant in Series 10 was a definite improvement, but that was reportedly more Capaldi's idea than Moffat's.