The "average" person who fly in the 60's is also not as old, more mobile, not as fat, and higher in the social spectrum (i.e. better educated) than the "average" person who flies today. [But not only do people have smaller and fewer carry-on, there's also larger seat pitch, so people probably can get into their seat more easily in the past.]

BTW, since the article mentioned Japan, here's an observation I had last Jan in NRT. DL and CO side-by-side. Both 777, the CO plane is 100% full, probably the same for the DL. DL has the "zone" boarding system - and the gate agent pulled out a huge white board and hand-wrote the procedure of the boarding. CO boards back to front.

Anyways, DL boarded, CO boarded. We both pulled out at around the same time. Both fast, efficient, and non-chaotic. At least on flights with a high percentage of Japanese travellers.

So, I'd agree with what the WSJ article concludes. No difference.