Hey I'm with you, I am a glass is half full type of person too. However I am also an artist and appreciate good artistic design, and I know how much of their heart and soul those imagineers put into designing those things
As a graphic designer, I heartily agree with this statement. What the general public, especially people who are not trained in art or design, don't realize is that an enormous amount of conceptual work, planning, and nitpicky decisions goes into good work. For example, internet users gasp in delight at well-done Flash movies, but few people recognize the time that planning the films--let alone making them--actually takes; and planning award-winning design layouts requires much more energy and brain power than actually creating them in a computer. Excellent designers take everything, from the spacing between letters (called "kerning") to the precise location of an object (your eye picks up location differences as small as 1/16 of an inch), extremely seriously. The average person enjoys the results without noticing the details.
What does this have to do with Epcot's and D-MGM's respective entrances? To put it plainly: The original designers put a great deal of effort, thought, research, and time into making the entrances to Epcot and D-MGM as grand, encompassing, and conceptual as they could. For someone else who has little-to-no knowledge of (or regard for) the original concepts and purposes to come along and slap cardboard-cutout, cheap "icons" onto the original works is, quite frankly, an insult.
That said, I think that Epcot's entrance and especially SSE need to be restored to their original designs. Regarding the hat...well, I actually like it. Not in its current location, of course; but it's a better icon for movie magic than the water tower (which I always considered a non-icon). Furthermore, the flashy Las Vegas casino-style design is part of D-MGM; the park is about Hollywood--perhaps the most fake, style-without-substance, glamour-driven location on earth; and we love it for that. But Epcot is about the "magic" of the real world. The wand is unnecessary at best, aesthetically destructive at worse.