ICQ was so wonderful to use then why did we flee to the next best thing to come along?

For the same reason we joined ICQ in the first place. Hype, incremental improvement, playing with new toys, and some of our friends were there but not on the previous thing we used.

ICQ did suck. It sucked the way most things suck: given the environment and state of the product at the time of release, they sucked less than other things on at least one metric.