"Modern" and "Futuristic" are not interchangeable terms.
Similar to how people often use the words "Modern" and "Contemporary" interchangably, though they too refer to distinct and different styles and time periods. "Futuristic" implies a further distant future than Contemporary reaches for, and Modern lags behind both, representing the mid-to-later 20th Century - ending right about the time that EPCOT Center opened.
Half of the intention of EPCOT Center was to jump forward from that design ethos - to leave Modern behind and leapfrog Contemporary for something yet unseen.
The reason people confuse these with regards to Future World is because so much design took note of EPCOT Center's architectural notions - in defying Contemporary it became an influential basis by which the term was redefined. That so many designers attempted to copy it with their Contemporary works does not make Future World a Contemporary work itself. And it certainly was never Modern.