The problem is the Earful Tower isn't always visible. It isn't in a prominent place in the park. Disney wants you to know you're in a Disney park as soon as you pass through the gates. And in order to follow the hub and spoke model, your weenie is smack dab in the center of the park.
The Chinese Theater was the weenie. It wasn't the icon of the entire park but it was the weenie you describe nonetheless. Both it and the Earful Tower described the two sections of the park. Chinese Theater was the basic icon of the Hollywood area, and the Earful Tower was the basic icon of the Studios. It may not have been in perfect sight, but that's simply the way the Imagineers designed it. Also, to add to that, Spaceship Earth is at the entrance to EPCOT Center, not in the center.
Plus, how does the hat represent the Golden Age of Disney and Hollywood other then being something that has Imagination and Magic associated with it?
Each of the four parks' icons have the meaning of each right on them.
Cinderella's Castle represents the timeless dreams we experience as humans, and timelessness is a theme that is all throughout the park (Fantasy, Past, Future, and Adventure are all timeless themes). The castle also represents how those dreams come true.
Spaceship Earth is a futuristic looking Earth, combining both themes of Future World and World Showcase. It also an homage to the centerpieces of the 1967 Montreal Expo and the 1939 New York World's Fair, and EPCOT Center itself, is supposed to be a "permanent World's Fair".
The Tree of Life represents a ton of things. It symbolizes how trees are the towers of life, and it also references the "world tree". On top of that, it also serves as an image from the Lion King.
The Hat just doesn't tell the story of DHS/MGM and it's Golden Hollywood themes as well as the Chinese Theater and the Earful Tower did.
Also to add, The Sorcerer's Hat doesn't hold anything special inside of it like the other icons do. Cinderella's Castle has a mural, a restaurant, and several unique shops. (and also the Dream Suite, but I'm not sure if they are using it for anything anymore). Spaceship Earth has, well, the Spaceship Earth attraction which does a great job at capturing the growth of humans, bringing the Future World and World Showcase together as one. The Tree of Life has it's tough to be a bug. (Although I admittingy would have preferred if they had a nature based show in there as originally planned, Eisner put ITTBAB in there just so it could market and advertise the movie, which at the time, had not been released yet). All the Sorcerer's Hat has is a pin shop. The Chinese Theater has the Great Movie Ride which perfectly captures the magic of movies. The Earful Tower has the Backlot Tour going around it, which used to be the heart of the Studios section of the park. (I admit this isn't a really important criticism, just something I wanted to bring up)
As for the tacky argument, I guess it's just the matter of opinion. That's just how I honestly feel about it.