Moffat needs to make the Doctor, the title character on this show, the STAR of this show. Not Clara's sidekick. Moffat admitted that Clara is basically the star of the show and that shouldn't be the case. I totally agree that he needs a companion of his own and inheriting Clara was a mistake.
Who knows, maybe Moffat wanted to go back to the original formula where companions like Barbara, Ian, and Susan were arguably the stars of the show and the Doctor was just kind of along for the ride.
Although personally I think we've still gotten to see
plenty of this new Doctor this season, even if he wasn't the main focus of the show.
I do agree though, as much as I like Clara, that Capaldi really needs his own unique companion next season. These two might be entertaining to watch together, but it still doesn't feel like the most
ideal type of companion for this Doctor.