The simple smiley emoticon - :) - is actually used quite a bit with Gen-Z (or maybe this is just my friends). I think because it's something a grandmother would text it simultaneously comes off as ironic and sincere because grandmothers are generally sincere.
Not Gen-Z but the one smiley I really hate is that "crying while laughing" one. I think it's the combination of the exaggerated face expression and it often accompanying irritating dumb posts on social media. I saw a couple too many examples of that to a point where I started to subconsciously see this emoji as a spam indicator.
(Cf. https://news.ycombinator.com/item?id=34663986)