This is not a problem in Japanese servers, but from what I read from these comments is the following:
"I can just do the minimal effort possible, I WANT to look at netflix/FB" or
"It's just a GAME, I can do what I want, it's my money"

So some people truly do this just because they want to be lazy. If this is not toxic behaviour I don't know what is. We all pay for this game, not only you. Please bring your best to dungeons. This kind of behaviour and thinking is a much bigger issue than a healer who doesn't dps because they're not confident, or they're new to the game, or the content simply doesn't allow for dpsing.