For me, at least, the problem is not that I had built up a deep and abiding affection for the fountain specifically. Suppose, last year, I'd met an imagineer who also thought the original Poly was wonderful, and who had been given the task of redesigning the lobby and other areas of the GCH, and who intended to carry over all the Tiki spirit of the original into the redesign. If the imagineer then told me that, for whatever reason, the original big fountain had to go, I'd be a little sad, but I wouldn't assume the redesign would be a failure.
What I'm seeing and hearing, though, suggests the redesign includes a desire to remove or soften the distinctive elements that made the resort unique. It's not that the fountain is going away, it's that it feels like the people who are taking it away don't see it as a loss, but rather as a cheesy element that needed to go, like old tacky wallpaper. In other words, it's not as though Disney is saying, "Did you love the old Polynesian? Don't worry, we're bringing it back better than ever!" Instead I feel like the message is, "Hey, did the thought of having the best monorail access make you consider spending $1,000 a night to stay in the Polynesian, but you didn't because you think pictures of the lobby made you think of the Brady Bunch? Guess what, we're watering down the theme, so you can stay here without embarrassment!"