Gen Z is having a moment right now with nostalgia for an era they didn't actually experience. It's also why Y2K and McBling (think 2004 Paris Hilton) is coming back. Between memberberry millennials who will never grow up and 20-somethings who've been told since birth that they'll never be able to own a home, society is romanticizing the time period to which Friends belongs. To someone who wasn't there or who was too young and ignorant to know better at the time, the 90s feels pretty peak. The 90s were pretty dang peak in a lot of ways so I get it.
The old person in me wants to complain about how fucking stupid it is to miss something you never had, particularly that period of time, but then I remember my generation did the same bullshit with "Flower Power" in the 90s. Plus if my culture was skibidi toilet and Mr Beast faces like Zoomers' is, I'd fantasize about being part of a superior time too I guess.
I agree with you, and I'll elaborate.
For Gen Z, you're right on the money that they're experiencing nostalgia for a time that they didn't even experience, which isn't even all that unique. Millennials did the same thing, and we didn't even confine it to a single era -- you mention the "flower power" '60s nostalgia, but nostalgia was being milked from the '70s (e.g., bellbottom pants and
That 70s Show) and the '80s (e.g., The countless "I love the '80s" shows that VH1 and MTV aired, plus movies set in the timeframe like
The Wedding Singer). as well. So, sure, it doesn't seem so crazy that those silly zoomers are now all into the '90s.
For millennials, we were just a bit younger than the characters of the show, so we looked up to them as aspirational. We were living with our parents and going to middle school while watching these cool young adults living exciting lives in the big city. We wanted to be just like them some day. Of course, it's unrealistic. How do these people afford their enormous apartments in NYC when they are rarely shown working and always hanging around a coffee shop? But we didn't recognize that -- we were stupid babies.
Fast forward to today, and the lives of many millennials did not turn out the way they imagined. Many are looking for some form of escape, so the nostalgia of watching that favorite show from childhood (which, any criticism of it is fair, but recognize that it held up a lot better than a lot of the other trash that came out in the time period -- I'm looking at things like the ABC "TGIF" lineup) and fantasizing about living like its characters, even if just for 22 minutes at a time.
That explains the continued popularity of the show but not the McD's toys. Why would a grown-ass adult want knock-off Funko pops of characters from their favorite TV show when they were 12? That I can't answer. Maybe they play with them the way that little kids used to play with action figures, doing the voices and recreating their favorite scenes. Or maybe they want to use them to decorate their office desks so that their coworkers can look puzzled and ask: "WHO is that character supposed to be? " I'd be embarrassed. But there are many people out there living without shame.