I think I miss most the fun of getting to visit a friend at the hospital when he was in an iron lung with polio. That was a real adventure for so many when I was a kid.
I'm sure a lot of grandparents are wistful over not getting to worry whether their grandkids are going to make it when they came down with rheumatic fever because the few antibiotics of the day couldn't get a handle on that strep that was "just a simple sore throat a few days ago".
But don't worry, massively drug resistant tuberculosis is making a surge, so we'll get a taste of the good old days again soon. Some may even get the joy of MRSA.
We tend to remember the good things, and ignore the stuff that was a little less pleasant.
I miss

those old signs, too, "No Coloreds". And sneaking up on that bunch of guys in their sheets burning the cross out in the middle of the swamp..... wondering what's up with that? And wondering why Pa's friends from work couldn't come visit us in our town, even though we could go to their house. He just told me, "You'll understand someday, son."
OH, WAIT! Racism's still alive and thriving. There's always someone different enough to bring out the hate in the narrowminded and insular amongst us. Heck, it was only a few generations ago the signs said, "No Ni**ers AND No Irish" right in NYC. And think, they both spoke English, even.
Nowdays it's even easier, since the hated don't speak the "accepted" language. Perish the thought they get a generation to acclimate the way many of our grandparents did, and their children become as American as everyone else, thus adding their own bit of flavor to the soup which is the real American culture.
Oh, wait, they were hated, too, for the same reasons; wrong language and cultural traditions.
So, at least that's a taste of the good old days that still persists.
Many years ago I worked for a man who was the most Christian man I have ever known. He said that one of the most important lessons in the Bible was one of the most overlooked: tolerance. I guess he was correct.
Where I come from:
My maternal grandparents both came to the US at the turn of the 20th century. Slovenians, neither spoke English when they arrived. The paternal side has roots that are Scots/Irish/English, and have been in this country since the 1600's, and fought in the Revolution. The wee bit that's the Cherokee in me, I don't know how long they've been here. Quite awhile. Their bad they tolerated the English speakers, I guess.
I live in a city of 100k. It is about 60+% Hispanic nowadays. Before I grew up a little bit as an adult a few years back, I resented them. Then I remembered this is a city of immigrants, and has been for many generations. People came looking for a better life, willing to struggle with the difficulties and the hatred so their kids would be better off. Sort of the same thing every parent hopes for. Makes us all alike in a very important respect; perhaps THE most important. That's why we put the welcome sign on the big statue in the harbor.
The Great Wheel continues to turn, and the name of that wheel is CHANGE. Realize that.
There's only one way to make it stay the same forever after, and I doubt you'll like that option.