Honestly the number 1 reason is pretty much what you highlighted OP , it was sold to me as Chrono Cross, the sequel to Chrono Trigger. Chrono Trigger is easily my favorite JRPG of all time to such a high degree that nothing else even touches it despite 22 years having elapsed since it's release. Obviously it would be hard to impress me with a sequel although now it would probably be worse ? CT has only managed to appreciate in worth for as I've aged. Back in 2000 though , it was intended to be the highlight of the "summer of Square" , 3 months that brought Legend of Mana (pretty looking but not much fun) , Vagrant Story (too far ahead of it's time for me to appreciate it ... essentially I found it too damn hard) , Dew Prism/threads of fate(which was a fine spiritual successor to Musashi but nothing jaw dropping) and finally Chrono Cross - a sequel to the "best game of all time".
Except... it wasn't really a sequel to Chrono Trigger so much as it was a re-make of the satalliview snes game Radical Dreamers. Elements felt shoehorned in to make it work as a followup to CT but it never felt natural to me. It reminded me of something like Dinosaur planet becoming star fox adventure - where you could tell this was chopped into a sequel rather than simply being it's own thing. The only element it retained from CT really was Yasunori Matsuda doing the soundtrack and I can admit - it's mostly fantastic stuff, some of his best work even. The pre-rendered backdrops and overall graphical presentation where stellar for a 2000 PS1 game too. But, it angered me immensely that it took the best mystery left from CT and just wasted it here. The game has like 50 characters that range from ugly to super ugly , all of them are incredibly weird. The story never really gets going or feels meaningful , instead trapped in some oddball state of vignettes that don't connect to one another in the slightest. Finally the battle system is a boring slog compared to the simple majesty of the original CT. Instead of tons of unique abilities you get color coded magic shared by everyone and - the hallmark of CT - double and triple techs, are relegated to a handful of techniques only possible with very specific parties.
The entire affair just felt kind of ... like a lot of nothing. It was just a strange journey with a rag tag regiment of oddball freaks and weirdos that don't matter and aren't important that are then duct taped to one or 2 plot threads from Chrono Trigger that were better left alone.
People will mention suikoden when talking about Chrono Cross due to the number of characters but the thing is , that game still had a core cast of decidedly likeable main characters and even in spite of that everyone you recruit had their own little story or reason for following you into battle. It was a different (much better) beast.
I genuinely believe Chrono Cross is the single most overated videogame in history. Even if I toss aside my personal issues with the game I can't see it as anything more than a very pretty but incredibly dull JRPG. There's nothing special about it outside of the music if you remove the name. It's not awful or anything , I mean it's not "legend of Dragoon" but really the only thing that memorable about it 17 years removed is how hyped up everyone was.
Honestly I'm happy for people that enjoy it beyond the aesthetics but for me , in all honesty - the closest thing there is a game that actually feels like a sequel to Chrono Trigger tonally - Grandia , the first one. These days of course you've got a few games that pay heavy homage to CT like "I am Setsuna" as well as "cosmic star heroine" and they're both great but I don't think any game will ever scratch that particular itch quite the same way.