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This is a common flawed reason to the "Vocaloid songs are better than modern songs" argument. Most likely people who say this haven't listened to such songs or don't know the English lyrics to them.

However this doesn't change the fact people would ignore this fact all together and say it just to sound like Vocaloid songs are, unlike "modern music", not all about love and sex which as you've stated is not entirely the case.

It's important to just ignore people like that all together since you know better.