It isn't a generational thing. The choice of emoji is a generational thing, but people of all ages do it. AI most certainly does not use emoji in the same way a young person does (unless you encourage it to, but even then it comes across as cringeworthy). If anything it's closer to how a middle-aged person uses them.

I'd also say the use of text emoticons has all but died out in anything other than ironic usage, or in situations where it's difficult to use unicode emoji (e.g. games or this very site)

When text is very obviously generated by AI it communicates to the reader that there is nothing of value to be read. It always writes in the same vapid, overly enthusiastic, overly verbose way. It's grating and generally conveys very little information per word. It's a cliché at this point, but if nobody bothered to write it then why would I bother to read it?