I remember standing the whole day at the 1982 GF
and it was jammed packed at the back of the seats where there was standing room.
As WP said the push for safer venues (all seated) reduced capacity of virtually every stadium around the world. Remember in the 1980s there were the horrible Bradford and Hillsbrough tragedies in England where a number of people died because they were trapped in old grandstands and terraces. It sent a message around the world about the need for safe sporting venues.
Here's a pic of the MCG in 1967 packed with 109k on GF day: