That is an amazing compliment! If there was a comparison to Taylor Swift or Ariana Grande, the vibrant couple would get context.
People vary. I’d heard of the Marx Brothers, and seen Groucho eyeglasses. Mostly because my neighbor’s father was a big fan. I’d heard of Fred Astaire. I still don’t recognize the names of the women you mention, and while i recognize Valentino’s name today, I wouldn’t have at their age.
Five.
Sorry. I went there. Because … Dope 
I knew the Marx Brothers in high school - my mother was a fan. But Coconuts came out closer to that time then Star Wars came out before today.
The real problem is that there are so many more people making content, even movie type content, today than there was back then. Then I had 7 TV channels, living in NY. Today, hundreds.
The number of movies and TV shows has exploded - the number of hours in the day to watch them has not.
I think, in addition to that, the ubiquity of ‘devices’ means that we each watch what we want to watch.
We of a certain age remember huddling together in front of the television, either watching what consensus decided we were watching, or … what Mom/Dad wanted to watch.
Born in 1968. Had not a clue who Merle Oberon was before looking her up and initially assumed it would be a man from the name (Merle Haggard, Merle Oberon). Know the rest and can vaguely picture Valentino in his iconic sheik outfit. Can vaguely picture Astaire in his iconic top hat. Can picture Clara Bow a bit better in multiple looks.
The three main Marx Brothers on the other hand are pretty seared into my brain because their old movies were still common on TV when I was a kid. Also 1950’s re-runs like I Love Lucy were someone like Harpo Marx might guest star were also ubiquitous when I was a kid in the 1970’s. They are by far the most identifiable I think for GenX like myself.
This is huge.
Up to about age 12 we had one TV. Tuned to our parent’s choices every night and us kids’ on Saturday mornings. But all of us kids across our age range had to watch that one thing.
Up to age 15 or so we had one record player / sound system. On which parents played what they wanted. I got my own clock radio / cassette player in my room at about age 12 and never did own a record player of my own.
Not so today.
I used to call the remote control device Die Macht. It’s what it was.
Neat-it’s like the Force in Star Wars; I remember watching it in German one time where old Ben kept saying that!
Möge die Macht mit dir sein.
May the force be with you.
The TV remote wielded tremendous power in my youth. That’s patently true*.
But …
When I was a child, I spoke, thought, and reasoned in childlike ways as we all do. But when I became a man, I left my childish ways behind …
…and got me a Jewish Space Laser.
*In fact, in the early TV remote days, it made a mechanical ‘click’ sound that could be frustrated/imitated by jangling a ring of keys.
[And to think: my high school guidance counselor said I’d never amount to anything]
Today, while at my volunteer job, I saw a woman who walked with a cane and was over 80 years old. She was also wearing a “Journey 2026 Tour” t-shirt.
She’s really not all that much older than me.
I wouldn’t had recognized most of them.
I was born in the early 60s and grew up in a family that first didn’t have a TV then had strict limits on watching TV.
And to be fair, before my daughter got into K-Pop, I could only name a couple of artists or groups. And while I know groups such as Blackpink, I can’t tell Lisa, Jennie, Jisoo and Rose apart.
It happened young for me. When I was a teen, I taught Sunday School at my church. When I was in my early thirties, I got pulled over by a cop who had been in my Sunday School class. I’ve felt olde ever since. LOL!
At that age, I knew of the Marx Brothers only because Gabe Kaplan used to regularly imitate Groucho on Welcome Back, Kotter. My parents told me that he was imitating “an old dead comedian.*” I actually came across a Marx Brothers movie on TV not long after that, and tried to watch it. I was bored silly.
- In fact, Groucho was still alive at that point, but he hadn’t been active in quite some time.
The flip side of Kids These Days not knowing a lot of older celebrities or works, is that there are a lot that they do know. Yeah, if you see a teenager listing to music on her device, it’s most likely to be Taylor Swift or Ariana Grande or the like, but it can be Bach or Lawrence Welk or Gregorian chant or Tuvalan throat-singing or pretty much anything else imaginable. A current teenager is probably more likely to know, say, turn-of-the-(twentieth)-century music than we were when we were teenagers.
You forgot Karl.
You are officially old when the coach of your Football (soccer) national team is a player you saw develop as an adult.
I’m being saved by the fact that Lionel Scaloni (PBUH) is 3 months younger than I.
In my case I felt officially old when the coach of my national team could theoretically have been my son (Julian Nagelsmann)…And now he’s even a retired national coach who could be my son. 
And Richard.
On a similar note: When LeBron James first appeared on the scene, he was that guy who skipped straight from high school to the pros. So he’s sort of fixed in my brain as early 20s or so.
And now he has a son playing, and is considering retirement.