I'm kind of surprised seeing Chrono Trigger praised for its exploration and *so much* optional content, especially if we are talking the SNES version.
I mean, I get the wonder of the epoch, and what optional content there is, is excellent. But it really isn't much, especially compared to other JRPG's. Nor is there a lot of exploration other than what you already visit in the story. For the optional story bits you even backtrack a lot as well. (Which is where the wonder of the time travel comes in)
Chrono Trigger is a tight, well designed JRPG experience and the OP and others here make it sound like a SAGA title.
Once you obtain the fully functional Epoch there is so much you can do (spoilers ahead). You can fight Lavos right away if you want or you can explore each time period and do the many side quests. You can save humanity from an evil genocidal computer. You can reforest a desert. You can help repair Marle's relationship with her father. You can help put to rest the ghost of a fallen knight. You can resurrect your dead companion.
That's a ton of optional content for a SNES RPG from the 90s.
See
Falksi
I'm fully aware how much there is to do in Chrono Trigger. Having 100% it 15+ times over the last 19 years (~10 on SNES and 5 on DS+ versions). And no, compared to bigger proponents it isn't. Their high quality, yes. But in pure amount of content it won't take you too long. Nor is there actually that much to explore. (And the optional locations aren't that big).
And again, a lot of it is backtracking and already combined with the story. Like resurrecting your dead companion sounds and is cool, but you're already directed by the story to it and tbh it's just another state to finish the game/fight Lavos in.
BUT let me stress this here:
That's not a bad thing.
First off, codex favourites like Fallout 1 aren't any different in this regard. Secondly I'd rather have a side-quest about a seed leading to a short QTE that saves Luca's Mom rather than 3+ additional 50 floor dungeons. Quality > Quantity.