'Normie' is a great example of how 'meme-culture' has permeated all circles, and we cannot escape it. 2-3 years ago it was used in certain twitter circles and on message boards, but now it is everywhere and used as a generic insult. This is just another version of 'boomer' or 'karen' . These terms are vapid/empty/meaningless, just like all other memes, and we should make a conscious effort to remove them from everyday usage. They are just the medium of communication, without a message.
I'll reach a bit more and say that a normie is typically someone who has qualities that a 'previous version of yourself' had. We look into the mirror and see a reflection of ourself and wish to shatter the mirror; the mirror breaks into many pieces but each shard still bears a fragment of ... yourself. You can't erase the previous you, but you can hate it insufficiently.
So - A Normie means different things to different people. How do you respond to people who live life in ways that appear less fulfilling than your own? It depends. If you are about the 'normie' your response should be measured and prod them towards leading a better life (e.g. get them outside and off 'drugs' like youtube). If you don't care about them, then respond with whatever seems appropriate. idk I have never thought about these things and am surprised people think about how to respond to comments like this.