Just to note, in my original post, I did not postulate that there are no new trends or that anyone, boys and men or otherwise, looks just the same as people did 30 or 40 years ago. Merely that a wider variety of fashions are available (and socially tolerated), and that in the last decade, few if any trends have been as ubiquitous as the “must-haves” of previous years. I am not oblivious to past and current trends; in fact I recognized new trends in real time when I noticed them come about, I would say starting in the late 80s at around 9 years old and definitely in the 90s and new 10s. In my original post, I even gave examples of the recent ones.
As a child of the 90s, I have to disagree that mens’ haircuts were no different back then than today. Maybe the closing years of the 90s, but at the beginning of the decade the way hair was cut tended to be rather different. Even if a man had short hair, it was common for more bulk to be left on and for less tapering to occur. If you look at pictures of men from the 80s and early 90s, they often have more hair in the back. Today if a man has even a little hair jutting out at the neck, people will call it a “mullet”. As for more iconically 90s trends, a popular haircut from when I was a pre-teen was the bowl cut. When did you last see one of these? During the course of the decade, hairstyles that were long on top and short on the sides (sometimes with writing or pictures shaved into the sides) were popular, or in general such where there was a lot of hair on top, parted in the middle and falling on the sides of the temples as curtains. Or long hair also parted in the middle a la Curt Cobain. Towards the end of the decade, however, short hair started becoming popular again. By around 2000, it way ubiquitous - when looking at boys and young men, you’d think it was the 50s all over again (and that was just when I was growing my hair out). At the turn of the century, there were lots of boys who had a sort of Caesar crop with the front spiked up. During the 00s, however, the skater look, where boys grew out their hair around the ears in a style not unlike 70s hair, also became popular. There was also the emo haircut that fell over the eyes, sometimes worn even by people who were not themselves emos. Today there doesn’t seem to be any typical hairstyle either on men or on women.
As for “normal” styles in the 90s, you’ll definitely see things on “Friends” and other period TV shows that are nowhere to be seen today. Examples are the “Rachel” hairstyle on, well, Rachel, baby-size short-sleeved cardigans worn over a woman’s top or dress, lipstick of a rather brownish shade, or severely plucked eyebrows. That said, I would say that 90s fashion was varied enough, and on average sober enough compared to that of the 70s and 80s that one could get the impression back then that people tended to look “normal” or that there was “no fashion”.

I’m sure that leggings are more common now than they used to be, among any age cohort, but I don’t know how much more common.
Leggings were popular in the 80s and more or less disappeared in the 90s with the dispersal of 80s fashion. They came back at the end of the 00s, around 2009. I remember that at that time they were quite popular in Prague; someone I knew from there who was not a big fan of them told me at that time that he had seen even more women wearing them in Brussels (IIRC), and that in many colors/patterns. I can’t say that nowadays I see tons of women or girls of any age in leggings. Now that I’m back in Prague, I see them here and there, but again, not as a prevalent fashion (they are kind of popular in one office I frequent). Back in Canada - the Toronto area, that is, I think I may have seen them a bit more often in recent years.
One good example that came to mind of my point that people nowadays tend to look any way they please: a year ago I saw a woman with a hairstyle that hasn’t been in style in some 30-35 years: what can basically be described as a fe-mullet, feathered all over and spiked on the crown, with bleached tips - something like what Olivia Newton John had circa 1982-3. This woman didn’t look older than about 40, perhaps less, thus not like someone who would have been of an age to have that hairstyle already in the 80s.