youngoldbloke
The older I get, the faster I used to be ...
The almost universal use of allen head bolts, or socket head screws, on bike components.
Another improvement are tyres.
Cannondale started selling their bicycle trailer, "The Bugger" in the mid-70's, IIRC.
On the other hand some things where we've gone backwards...
- Fugly bikes with sloping top tubes (just wrong), plastered in stickers to make them look like advertising hoardings.
Wrong, it is so the whole world can see you making a tit of yourself .Head cams. Now you can go looking for trouble AND have the evidence!