That’s an impressive memory for a couple of trips over 40 years ago. You must have been very lucky or were smart enough to visit in a weekday. As
@deejdigsdis mentioned, the line for Space could take up almost the entire upper deck, and before they enclosed that space for the theatre, the line could snake well out into Tomorrowland. Heck, that standby line can get to 60 minutes before noon on even a slow day these days.
But, to place things in proper context, I never said the Park was
always busier, just that busy days were often busier. No AP’s and different visiting habits in general meant fewer weekday visits (the Park was actually closed 2 days a week until the mid eighties), plus shorter operating hours, meant going to
Disneyland was more of a weekend or holiday trip for many, which meant larger attendance swings and serious congestion on certain days, while other days (like a Wednesday, maybe) could be downright empty.