You can talk about the off seasons Lewandowski, Benzema etc. have had, but fact is, they're still on top of their game NOW and show little to no signs of slowing down. Kane on the other hand looks like shit.
They had off seasons/periods in their career, and then recovered. Perfectly possible Kane will do the same, but you're declaring him totally done, and marking out seasons where he exceeded xG and ones where he was top scorer/top assister as part of his decline because of 'advanced metrics' which other top strikers having top seasons have looked similar in.
Awful start to the season, but some aren't ready to declare him shot as a player because of it, you obviously are. Only time will tell who is right.