It is never good to force a player to stay at a club that he don't wants to be at anymore because it has several negative aspects. First of all the player is probably not happy at all and for a good performance on the pitch a players needs to have a positive attitude, confidence and a focus on the game. Secondly the relationship to the fans is probably destroyed or at least harmed, i don't follow the english premier league that closely but i could imagine that Kane is not cheered on that much as he was before that drama. And another point is that the club, Tottenham, probably won't get as much money now for Kane as they would have get back in the summer.
Kane is obviously a player that is very very well talented and it is normal that he could move to a team that would be a lot better for his talents. However, Kane doesn't seem like "upset" just because he stayed at the team, I mean it is more like "so-so" situation for him. If he leaves to a great club and gets paid a lot then he would be happy and if he doesn't leave and stays there he would still be quite happy about it as well and nothing would really change.
I doubt that there is a good case to be made about this situation, there have been a lot of players like that before that had a transfer and I doubt that people talked about them this much. Hopefully I would say that Kane would end up with the best decision but I think nothing would really change much.