Untrue. It was enormously successful when it opened, and retained an extremely high level of success and attendance throughout the entirety of the 80's and even early-mid 90's. This was well before the Food and Booze events were conceived as well that are now responsible for driving attendance instead of actual substance. People like
@marni1971 have mentioned on numerous occasions that EPCOT was a huge and immensely successful project before poor decisions lead the park down a different path. EPCOT's huge success and profitability was an immense boon to the Disney company during the years when their film studios were going through a somewhat rough time.
Here's a video from 1989 showing a truly packed EPCOT Center in its glory days, still ridiculously successful even years after it originally opened (and this was taken shortly after MGM Studios had opened the same year).
Literally every open ride there demonstrates long lines spilling over out the door, and this was long before they began to close the classics like Imagination, Horizons and World of Motion. It's even more impressive considering how many of those rides were so ridiculously efficient and high capacity people eaters.