Procaine, better known as Novocaine, was in wide use from the 1910s onward. Unless you had your teeth pulled by a blacksmith, that's what you'd get, right up until the 1970s.
I'd miss clumping cat litter, without question the most important invention of the 20th Century. I can't think of much else I'd sincerely miss.
People not smoking: I think I could adjust to almost everything, but I couldn't return to that world where smoke was everywhere (like in the 1960s and most of the 70s). Just today, I walked by a single smoker on the street and it reminded me of how disgusting all that smoking used to be (and not just on the streets, but in offices, stores, restaurants and airplanes and even peoples homes). Ugh.
I'd miss the internet, but would adjust to just using the good old US mail service to shop for hard to find items...
You could get anything from...a rebuilt Model T engine to spermicidal jelly from the Sears catalog.
I'd miss a bunch of things, no question about it. Air conditioning, access to higher education, television sports broadcasts, reliable outboard engines, modern air travel, modern navigational aids, internet shopping, automobiles that run for more than 75,000 miles....I’d miss these and many other things greatly.
But I'm getting to the age now where modern medical care is very important to me. I'm guessing that's what I'd miss most.
AF
...Will they look back in wonder at a time when people had to actually drive the darned things?