At his worst, Kane's effort levels were shockingly bad, he ducked out of headers and tackles, and he definitely stopped showing for the ball. Also his assists dried up completely (3 in 38) and you could find around about 10 goals in our net that wouldn't have happened if he was shutting down from the top. However, he still got 30 goals and for some fans accepted this very big compromise. I didn't.
When Ange came along, I had a feeling we might be in a tough place with Sonny. Roll back 20 years and a Son / Solanke partnership would actually be OK in a 4-4-2. Ditto Son and Kane. What we're now finding is that Sonny can't excel in a Ange's system. Son is basically WYSIWYG - what you see is what you get. Unlike Kane, he hasn't got the brain to learn new tricks and that is proved out over 5 different managers who can't get his brain in gear for defending in his own half. It's the same with the wide forward play we need.
I agree what Brain and others have said in that he should eventually end up on the bench. It will also help Spurs to find a plan B if we have someone that doesn't quite fit the system that the opposition have just got used to over 60-65 mins. Son coming on will pose a very different threat from wide forwards.
Also, we need to find a better captain.