From what I understand, attendance last year wasn't that far off from when it peaked in 1987. The attractions did play a large part, but for the 80s at least the park was new and tickets were half the cost w/ inflation as well. Also consider that it peaked again in 1997, despite World of Motion closing, UoE being downgraded to Ellen's, and no major changes to the other major attractions in over 8 years or more. Attendance is trending upwards again, and at least for the few years after the new attractions open, it'll continue.
Also, Disney is probably making way more money off Epcot now with higher ticket/food/merch prices and the festivals eating up cash.