Well, with the advent of FastPass and now Lightning Lane/Genie+, the queues are hold fewer people in general, because a 60 minute wait if half of the capacity is going to Genie+ means the queue only contains half as many people for that 60 minute wait as it would if there was no Genie+.
This isn't a complaint about Genie+ and I don't want to go down that path -- just pointing out that it significantly changes the math around how many people are queueing. There are also the guests who only use ILLs and Genie+ and never queue for anything, so they spend most of their park time just milling about and increasing crowding while waiting for their next time.
Because the capacity was so high at those original EPCOT attractions, and they still generally had 30-45 minute waits (sometimes longer), they were taking far more people out of the park at any given time than what's currently offered at EPCOT due to the combination of shorter ride experiences and Lightning Lane/Genie+.
Even now, if Spaceship Earth has a legitimate 15-20 minute wait, it's occupying about as many guests as (possibly more than) Frozen Ever After does with like a 60-70 minute wait.