There were alot of factors, many considered it wasnt as good as chrono trigger, its a post ffvii rpg, it was released right at the end of the ps1's life (same thing happened to ffix)
I enjoyed it, dont think it deserves hate
I did find the gameplay a bit unintuitive, especially figuring out how magic works. Plus, attacks miss quite often. I'm not the biggest JRPG person by any stretch, so straightfoward games like Grandia or Dragon Quest hook me in faster. Despite all that, I really appreciate how bold and creative Squaresoft got with Chrono Cross. It's not "just Chrono Trigger 2" by any stretch.
@Robert Newbie that's the thing it was never meant to be a sequel nor is it, it's more or less a spinoff according to an interview, as the main dev refers it to be an entry to the chrono series but isn't a sequel, he tried making it very clear as trying to name serge crono results in it not letting you do so, it's not uncommon for spinoffs to fill build upon past entries look at kh
I've heard rumors, like it was never meant to be a Chrono game in the first place. It seems that it was always meant to be one and that the team didn't want a direct sequel. They wanted to focus on Schala.
It was great to deviate because Chrono Cross stands on its own merits as much as it does as a Chrono game. Creative times for Squaresoft, from Parasite Eve to Xenogears to Brave Fencer Musashi.