Let me ask you the question I always ask people who express this opinion:
What year did you start reading the Marvel books?
For the sake of argument, let’s say that it was 1983.
And let’s also say that your preferred passage of time was in effect from the beginning.
At the point where you started reading, Spider-Man was on the cusp of becoming forty, as was the Human Torch. Iron Man was in his fifties, with greying hair. The X-Men were middle aged. And so forth. (Which is better than the DC heroes. Batman at this point needs a walker to get around Gotham.)
These are not the characters that you fell in love with, and that you created a lifelong bond with.
And suggesting that we “just create new characters” is asking more than you seem to think. People have been trying to create another character as successful as Spider-Man since 1962, with very little success. And Spider-Man existing doesn’t prevent anybody from coming up with the next Spider-Man either.
Suggesting that kids just read the old comics is also a bit of a stretch. Tastes change, and people always want what’s new, what comes next. Do 1950s comics satisfy you like new ones? Why not just read the old ones?
This all really comes down to wanting the characters to grow old with you, to reflect your own experiences. And that’s a personal desire, but it’s also a selfish one.
Spider-Man belongs to the ages, to all generations, not just one generation. He will live on long after you and I are dust.