Honestly, personally I don't know if Harry Kane is really experiencing a curse or not but certainly this is a very unfortunate situation because in the end he failed again to win the title at the end of the season with his team, but overall yes we all have to admit that Xabi Alonso's squad is truly extraordinary this season, they can always secure matches by winning 3 full points or a draw and also become one of the teams that managed to score an unbeaten record since the start of the season began. On the other hand yes I am quite worried about Harry Kane there, what I mean is that I am worried that Harry Kane will be sold because of this season's failure, but I think it's too early to conclude now.
Harry Kane experiencing a curse is just a banter among fans. People call it "curse" or "luck", because those happens on unexplainable situation. There were many players who have similar bad luck of not winning certain trophy, like Zlatan Ibrahimovic and Ronaldo Nazario who never won Champions League. This sounds unfair to the players, because trophies are not individual achievements in football.
Harry Kane still have chances to win the league trophies, because he will still play for Bayern next few season, and Leverkusen won't always have this remarkable league campaign. Next season, Bayern need to have a very good start of the season, if they don't want to go under pressure if Leverkusen or other team taking the lead of the league early.