Bayern Munich were considered as one of best candidates to win Champions League after they purchased Harry Kane from Tottenham Hotspur until recent weeks they shown some terrible performances.
Arsenal have never been a good candidate to win Champions League and they are even far lower than Bayern Munich in tradition and quality. Porto won one Champions League with Jose Mourinho but Arsenal did not win any Champions League. They got a final match but lost to Barcelona.
The problem isn't about Harry Kane as well. Because he is currently the best performing player in the team. He has scored a lot of goals to help this team achieve titles. But he is still really unlucky about winning a league title.

Even at a team like Bayern Munich he has found the season in which Bayern Munich play worse as a team. The title streak in the Bundesliga is about to end.
Arsenal are of course not one of number one contenders. They have a great scoring potential this season as you can see from their performance in the Premier League. But they are a very young team and it adds extra difficulty when it comes to winning a Champions League title. Consistency problems are seen clearly like in the Porto game.
When did Harry Kane joined the team? Why would fans feel that he is part Of the problem the team is facing now. Yes, they may have had the joy that he would bring about more improvement in the team and instead Bayern Munich is still underperforming compared to there level. However before now Bayern has been going through this problem before Harry Kane came to the league and the manager should try to fix this problem instead of poor Hary Kane going through some emotion blackmail via the posts on social media that ever since he came it has been nothing but failure for Bayern.