I’m not @Jophiel but my take is …
“Jeans” means “Long pants made from denim-like fabric of any color”. Of course “blue jeans” have to be that iconic Levi dark blue. Jeans in any other shade of blue, e.g. sky blue, might be jeans that are blue, but cannot be “bluejeans” which is functionally a single word.
Exactly. The topic isn’t “list things people no longer do”, it is specifically things that were once concidered cool. Wearing a Member’s Only jacket over a Panama Jack shirt? Once cool. Writing out a paper check? Not something that was ever thought of a cool.
I play in a popular Grateful Dead tribute band in a major city. When I joined, I expected to be playing in rooms filled with people over 50, but that really only accounts for about half the crowd, the rest are college-aged, and most of them are wearing jeans. We see new young faces each time, and it is rather heartening to see the youngsters grooving to the music just as much as the older folks. I think they just really enjoy seeing actual musicians playing real instruments.
Rollerblades & roller skates.
I most often see them wearing sweats or joggers. Pajamas are more on girls but I do see some guys wearing baggy plaid bottoms. It’s not that they’re wearing black denim pants, they’re (usually) not wearing denim at all.
I’m flexible on color but, if they’re not made of denim, they’re not jeans.
Of course, I’m not speaking authoritatively for the world or anything. Just my observations of middle/high school students at a suburban Chicago school.
RE: cargo pants
My son ( age 50) stopped wearing jeans because he could not carry a set of car keys a wallet and an i-phone in his pockets easily. Instead he switched to shorts or cargo pants and carried a “bag” that looks like a cross–body type “purse”. He can pull this off because he is 6’5” and in excellent shape. Tall people just do what they want.
Got it. But it veered into that territory.
Probably by me.
I’ll go now.
If he’s interested in old rock, he should give a listen to The Move, pre ELO with most of the members. Good 60s shit that never crossed the pond.
What was old is new again.
More or less what the OP asked for hasnt really happened much.
Square dancing. 
It’s one of my hobbies, and most of the people i dance with are young. But I’m general, it was much more popular in the 50s-80s, and i think it was actually cool in the 50s. Now it’s definitely something mostly done by old people. I went to a dance weekend last week, and was one of the younger people there.
Yes, true. I was just thinking king along the lines of things that may seem geezer now. I wasn’t really thinking about how cool they may have seemed.
Harley Davidson Motorcycles?
I’m not a rider - my wife wanted to be, and got her license, but never bought her own bike (rode friend’s bikes though). This was 15-20 years ago, and even then, that crew (early 30s) saw HD as a “geezer” bike - too big, too heavy, faaaaar too expensive - bikes that only 50+ old, rich, white guys rode.
Given the HD riders I’ve seen since then, that remains true. Sure, there are some newer riders, who love the heritage and history, but I think they fit the OP well.
Just wait until you have back trouble.
Yes, this is exactly why we do it. Once you’re in the back-pain club, you notice people doing it all the time. I try to grab a cart from the parking lot on my way in so I can get a head start on leaning over it. (Also to make myself more visible to cars.)
But i don’t think leaning on a cart (or using a cane, for that matter) has ever been cool.
I’ve got a coworker in his early 20s whose favorite musician of all time is Paul Simon. The easy access to music on demand these days has made it a lot more accessible (and acceptable) for young people to get into older bands, as opposed to when I, a ‘90s teen, was considered impossibly square for being into bands like the Who and Blue Oyster Cult.
Dungarees (USian: overalls) seem to be having a moment here with the youth. Other than that, when it comes to male trousers I see far more chinos, cargoes, hippy-style stripey drawstring pants and saggy-crotch ĥarem pants than denim jeans overall, but jeans outnumber any individual other option. This is with my kids’ 13-21 crowds.
The young women wear not-jeans at least 10 or 12 times more than they do denim. Except the metalheads, where it’s half jeans, half cargoes.
I am not a big jazz fan, but I think at least hard-rock is not going anywhere. Listen to Hank Williams III, the grandson of the famous Hank Williams for a hard-rock/country mash-up… He’s profane, but he is good.
Since people are debating denim jeans —one thing I have NOT seen anyone wear recently are denim vests–particularly the ones that patches of hard rock/heavy metal bands all over them.
Denim shirts were cool back in the 70’s but not so much any more, dates you as a geezer I suppose. Also wide white belts with blue jeans were cool at the same time but I don’t see anyone wearing them much with jeans. And bell bottoms have come and gone along couple of times.
That was my main dress from age 12-28, denim jeans and jacket, and though I’ve always been a rocker, I’m not especially a metal head. Denim vests or jackets have gone out of fashion around the time I stopped wearing them, so middle to late 90s. And FWIW, I always found denim shirts to be ugly. Now I think only squares still wear them.