That doesn't clarify anything, I'm afraid. In what possible way is Final Fantasy not a JRPG anymore? I mean, given they're continuing with it in 16 it's probably safe to say it's transitioned into being an action-RPG series at this point, but that's far from unheard of, with things like the Tales series or Kingdom Hearts being longstanding action-JRPG franchises, so all that is is a subgenre shift. And if you're not talking about that, I honestly have no clue what you think you're saying with that remark.
JRPGs have always been niche games, aside from specifically Final Fantasy, mostly (to my understanding at least) because of how huge FF7 made that series. Or Dragon Quest if you live in Japan, I suppose, but for the rest of us, no, Final Fantasy's the only one that's popular enough to break out of the niche status.
I don't know, maybe Persona's starting to these days, but I don't feel too confident on that front just yet.
Okay, Chrono Trigger I have played, and honestly, while it's certainly a good game that I enjoyed, I don't see what you're talking about there at all. There's nothing about it that I'd hold up over many other JRPGs. Certainly I think there's plenty of better ones out there. It was probably one of the best at the time it came out, but now? Not even close, IMO.
Definitely not happening anytime soon - my plan is that after I finish up my War of the Chosen run it's finally time for me to play through Persona 4 Golden, since I didn't want to jump right into that when it dropped just as I was finishing Persona 5 Royal back in June. And... honestly, I don't know. I've seen people praise it on here before, obviously, but aside from the general amount of love it gets like that, when I've seen specifics, they've never made me feel like I wanted to play it. Things like talking about how the combat is the worst part of it and you want to just avoid it don't exactly get me raring to play a game, for example.
(Also, Witcher 3 comparison is another that doesn't work for me, haven't played that. Deliberately chose to skip it since it does the whole open-world thing that I'm just not into.)
Kind of another example of what I mean about specifics not making me want to play it there. Maybe there's something to the presentation of it that makes that appealing in some way in context - there's certainly games that can get dark like that and still be appealing to me in the moment - but I don't think just talking about it like that is selling it the way you seem to think it is. It just makes it sound morbid and unpleasant.