Cheers for the comment, but honestly, I’m 40 years old and couldn’t care less about downvotes.

To elaborate a little on my earlier opinion, I think the story required an actor who can (a) do a convincing American accent, and (b) present somewhat convincingly as a paragon of gruff masculinity. In my opinion — and it appears I’m in a minority — Cumberbatch can do neither. He exudes weirdness and alienness no matter how much dirt and grime you cover with him.

Generally, I like Cumberbatch. More often than not, I like his work. I just think he was a bad fit for this role. Verbally, the accent is distractingly bad. In terms of the general vibes he gives off, he’s too peculiar and otherworldly. That works brilliantly for him in other roles (Sherlock, Imitation Game, etc.), but not this one. The twist would work better with an actor who doesn’t give off those off-kilter vibes from the moment you see him. Again, just my opinion. Few, it seems, agree!

As for finding the film slow and dull, I will say that I’ve seen it only once, and perhaps I wasn’t in the right mood. FWIW, I remember thinking the same about The Assassination of Jesse James by the Coward Robert Ford (2007) when I first saw it. I re-watched it earlier this year, and now I’ll tell anyone who cares to listen that it’s one of the best American films of the last 20 years. Perhaps Dog will 'improve' on subsequent viewings in a similar way. Both films have a similar vibe.