To be fair, he took awhile to get going. Now he's plugging along nicely because the writers have finally pinned down his personality, but for a lot of series 8 it was like they were trying so hard to make him crotchety and dismissive that it wasn't endearing...it was just weird. I get that they wanted to get away from Matt Smith's more "cuddly" Doctor but they went far in the opposite direction and didn't take the viewers with them. It's especially evident when you binge-watch series 8 that it took awhile for the writers to settle on his personality.
Contrast that to Matt Smith, who hooked me inside 30 minutes, it took me most of series 8 to enjoy Capaldi's Doctor. And while I do feel that he's settled in nicely now, I think a lot of viewers are still on the fence. Maybe some of it has to do with age, I don't know.
While I will loyally watch and I still enjoy the show, I haven't been excited for each episode since series 7B. I do like Capaldi and his fun interaction with Jenna but the episodes themselves just aren't as fun anymore. It feels like it did at the tail end of RTD's run. I think the series either needs new blood (showrunner) or a new direction.