I agree that RoE is pretty old and, as much as I love it and don't want it to, it probably should be changed. But I wouldn't say it's "dated" at all. The technology of the globe still amazes me, the music is breathtaking, and the story is inspiring. World of Color is amazing, no doubt, but it's still just projections of cartoons on water, which is a huge chunk of Fantasmic too. RoE is WAY more than that.
To be fair, I haven't seen WoC in person yet, and I'm not as emotionally attached to the Disney movies as I am the parks, but I just can't imagine it being "better" than Illuminations.