I think it's a mix of this, and the injuries/motivational issues. Spurs are and have been in inertia for a little while, and Kane has been in and out of football with constant niggling injuries. He just looks like he's lacking that killer instinct and sharpness his game had 18-24 months ago. The lack of a cohesive Spurs unit is only exemplifying this.
I noticed ever since the World Cup, he's been playing in this strange, almost supplementary 9.5 position. I don't know if that's a personal want for him to become more involved in build-up, or if it's a tactical thing from the manager. Whilst he does have good technical ability for a striker, Harry Kane is blatantly at his best as close to the opposition goal as possible, taking as many shots as possible. Having the best finisher in the league taking fewer shots and fewer touches in the box isn't going to work well.
I am a big Kane fan, and do believe he's a fair bit better than Abludclartyang at his very best. Not sure he's shown his best in a while, though. And in the last 12 months, Auba has definitely better the better striker.