Comparing PLATO to today's systems exemplifies the old quote "Software is a gas: It expands to fill its container".
I used a PLATO system during the last couple of years that it still ran on an old CDC Cyber mainframe (which the university was barely able to keep stringing along with spare parts getting scarce).
PLATO usually ran relatively smoothly with up to 400 people simultaneously logged in to interactive sessions via serial links. At any given moment, they were all sharing a single processing unit with integer speed probably comparable to a 80386, and less than 1 megabyte of magnetic core memory. It was an incredible feat of efficient programming.
In contrast, recently I was finally forced to upgrade my 5-year old cellphone because it was getting to the point where it often couldn't fit a single app for a single user in its 3000 megabytes of memory without swapping out all of the other apps (particularly annoying when one of the other apps is the music player). It ran smoothly when it was new, but with software bloat compounding exponentially with each update, it was getting to be as slow as molasses.
This was even though I had at least one million times as much memory allocated for my personal use as I did using PLATO. Now that my new phone has *three* million times as much memory allocated to me as PLATO did, things are running smoothly again -- for now.