Instead of saying "this game sucks, it's boring, and too hard!", try "this game isn't for me, I don't find it interesting and the difficulty doesn't match my playstyle".

If you go on and say that games I like is objectively shit, you are wrong and should feel bad.

You can criticise all you want, but hopefully you realise that your thoughts are just your own opinions and people will disagree with you.

Tl;dr Just because you think a game is bad, doesn't mean it's bad.