Elder millennial here. Personally I view this as the kind of good natured ribbing that comes from a healthy relationship between an older and younger sibling. I think our generation (and Gen X too) have an overall positive view of Gen Z, but you are out of your mind if you think we’re going to pass up an opportunity to give them some shit when it’s warranted!
Rainmanslim’s comment doesn’t strike me as mean-spirited at all. If anything it’s the opposite of condescending because it acknowledges that the cringiness of being a teenager knows no generational bounds. Embrace it and enjoy it, and then enjoy it again when you’re old enough to laugh at your younger self!