I don't necessarily disagree with your assessment of the Bay Area. But as somebody who remembers Great America from its beginning, things were different all around compared to today. Also, 1976 being the US bicentennial, doesn't stretch the imagination that the park developers (Marriott back then) wanted to leverage the event and overall positive sentiment.

But ignoring the patriotism angle, back then, to the best of my recollection, Marriott actually made a legitimate effort sticking to the park theming to try to give you a sense you were walking into another world (similar to the Disney approach). Each "land" (e.g. Hometown Square, Yankee Harbor, Yukon Territory, Orleans Place), was themed to a different US historical period, and the buildings, rides, decorations, and even the restaurants/food made a stronger effort to adhere to the historical themes in each land than they do today. You didn't need to feel patriotism in order to enjoy the immersion of being in a fantasy historical period/place.

In contrast, the last time I strolled through Great America, I got no sense of any theme, nor feeling that I have walked into another world. Ironically, the thing I remember most is the Claw Crane Machines were touting you could win iPhones. So instead of being able to escape into a fantasy reality, this really kept me stuck in the reality of our normal world.