I try my best to ignore anyone who says Kane is shit/overrated/whatever but as troll bait goes, it's fucking catnip to me. He's my all-time favourite player, yet I'm completely honest about the bias that can create (unfortunately it doesn't go without saying that most people declare their biases and try to correct for them -- quite the opposite). I can't help myself a lot of the time, even in YouTube comments (where you've lost the argument as soon as you join it).Yep, I would say I’m continually shocked by people under estimating him, his worth to us and his ability, but I’m not, there’s so many people who don’t have a clue.
I always say if people don’t rate Harry Kane then they don’t really know the sport and it’s utterly pointless discussing it with them. He’s one of the best English strikers every with a goal scoring per game record similar for England as jimmy greaves and in the PL similar to Aguero. It’s utterly insane people don’t rate him and want to sell him. Insane.
It's been my experience that people who don't rate Kane usually fall into one or more of three categories: (a) they're doing it for the contrarianism/troll value and/or have anti-Kane biases (e.g. anti-England types), (b) they don't watch many or any Spurs or England games, (c) they don't know much about football.
(a), usually combined with (b), is very common outside of Spurs communities, since a lot of people don't support/like Spurs and actively dislike England. And a lot of people judge Kane on the fact that he never looks (or sounds) like the archetypal flashy superstar striker on the pitch or off of it.
Naturally, (c) is by far the most common among Spurs supporters. A lot of these ones don't, for example, get that Kane creates tons of space for the other attackers even when he doesn't touch the ball at any point during a move, giving the impression of him doing/achieving very little when he actually is.
ETA: As Pzabbythethird correctly identifies above, the younger generation also has a bad habit of getting their "knowledge" of players and/or clubs outside their own entirely from video games. It falls under (b) and probably (c) and maybe even (a). In many ways, the "knowledge" those kids have is worse than no knowledge at all. At least you can't be wrong about what you recognise that you don't know.