Most of the big differences are noted above - smoking, aircraft not as full, wide body aircraft on short domestic routes, easy security etc one other item was the ease with which you could jump between airlines. Before 78 you could literally just go to the airport and ask for the next flight to LGA and whichever airline had the next flight would sell you a ticket. After 78 that changed a bit but it was still was in the 80s to get put on a different airline if your flight was cancelled or delayed. That still happens today - sometimes. But it was no big deal in the 80s.
Another 80s thing was overbooking. The airlines still do that today but in the 80s they weren't very good at it. And when you got bumped you were often paid in cash on the spot.