When others say thank you like me, should I answer nothing or be impolite? Which is more polite?

It seems that nothing is popular now. Supposedly, the "standard answer" should be "you're welcome", "you're welcome" and "you should". I don't know when the standard answer became "nothing". At first, I was not used to it. I feel as if I have made some mistakes. I went to apologize and others forgave me.