Superman had as much trouble keeping Jimmy Olsen the Amazing Frog Boy out of trouble as unpowered Jimmy, because Jimmy is the definition of a civilian. He's not qualified to participate in Superman's adventures. Wyatt Wingfoot has both the education, and the physical prowess to go anywhere and do anything with the Fantastic Four. Both characters had as part of their origins exactly that mix. Thus, Wyatt is not a civilian, while Jimmy Olsen can't be anything else.
Wyatt Wingfoot is just some dude. He gets into adventures because he happens to be hanging out with Johnny when weird stuff pops up, not because anyone ever thinks it's a good idea to bring him along to fight Dr. Doom. If we're using the fact that Superman has to save Jimmy as the measure, look to how many F4 stories would wind up with him dead if Johnny wasn't around.
You'd be surprised how quickly those ties disappear whenever any major change occurs. It happens in real life, and that's why it happens in fiction.
Why in the world would they abandon their friends just because they now have what is essentially, from their perspective, a new job? Does that really match the personalities of most superhero characters?
Even if they did, why would that even matter to supervillains? Are they going to think, "Oh, sure, this guy was my enemy's close friend since childhood, but since they don't hang out much anymore, I guess they're completely useless to me as a hostage. Welp, on to the next plan?"
Uncle Jacob and Aunt Petunia live in Arizona, and most of the world thinks Ben Grimm made them up.
He's a public figure. Anyone can check up on whether his relatives exist. I don't see what Arizona has to do with anything. Most of the F4's enemies can pretty easily get there.
She-Hulk's dad is a cop, and her law firm buddies don't socialize with her (or they didn't. She had to date Wyatt Wingfoot because no one else would come near her).
And a cop can handle the kinds of supervillains she faces? In her more recent runs, she's had co-worker friends.
Luke Cage never amounted to enough to get Doctor Octopus's attention until bad writers contracted small world syndrome.
So? Small time supervillains can harm loved ones, too. If anything, super-mobsters seem more likely to target your friends than your Skrull Empires and Galactuses are.
(That reminds me of an amusing issue of Astro City, about a comic publisher who publishes "based on a true story" stories about the heroes. He specifically only does stories about huge, cosmic threat-type villains because they're not going to care, or even be aware of, what some funnybook publisher is writing about them. Twist: Turns out one of them does care.)
"Captain" Marvel (I hate that name for her) and her family know the score from her secret agent and test pilot days.
Ah, so it's all about knowing the score. In that case, that's a reason for heroes to let their loved ones in on their secrets, not to hide it from them. They should make sure their friends and family know the score.
In any case, those specific characters were just examples off the top of my head. There's plenty more. All I'll say is that the Marvel universe you're describing where superheroes with public IDs don't make friends with ordinary people is not the one I recognize.
I'll skip the whole bit about aging fans. I don't see how what that has to do with anything. Superheroes without secret identities have been around for decades, including back when superhero comics were entirely all-ages.
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