It's really simple.
they won't be until another one catches on.
the big boom of JRPGs came around when Japanese/Anime designs was the shit. In the 90's it was the new obscure cool stuff that you didn't get easily over in the US and thus it became popular. Even Western created stuff tried to ape it. But then as time went on, it became more prevelant and the "shitty" aspects of it became more prevekant as well and eventually tastes changed. This is an industry that simply chases the next big thing. It was platforming mascots, then anime, and currently War FPSs. The market was simply flooded w/ JRPGs and the mass market simply had their fill.
Things like moe designs and archaic design plays a role too...but some of the older RPGs had the same "creepy" aspects to it, the same tropes, and so on. The industry just simply grew out of that phase or rather those that loved it did and moved on. Making it a niche genre.
That being said, simply making them into WRPGs where the main leads are middle aged dudes with beards who brood and have sex, isn't exactly the answer. I think there is room for both. Star Ocean 4 is horrible and that is the type of shit I don't like. The "characters" in that game were litterally tropes and moe blobs, and even as a guy who watches a lot of anime it was cringe worthy. but the Tales games? Doesn't bother me. It's childish. It's anime as fuck. But that's fine because that's what I go to those games for. It can get better as Graces bored me to tears plotwise (my ps3 also died...and I didn't want to get back...as I would have beated it). But the issue there wasn't that there was tropes it was that they were bland. Symphonia is trope tastic but I love that cast because they were enjoyable. So in the end it comes down to what you like.
I think the idea of making every genre mass appeal is stupid and it only ends in everything being the same. Super serious, brown, standard games with "emotional depth". We don't even get that many JRPGs anymore and the ones we get aren't all "ugguu am I kawaiiiiiii" games. Hell even the Atelier games aren't that. There should be room for those games, anime as fuck games, super serial games, JPOP games. That's one of my favoprite things about thsi industry, there are games for everyone..instead of games that sell well to the majority. I like that Japanese games are Japanese, not everything needs to be focused on western tastes and if you don't like them...then play something else instead of wanting to force games you don't like into beign what you do like.
now I'm not saying they haven't fell on hard times as It is difficult to think of one JRPG that I liked from this gen...hell the best one is a port of a ps2 game in Persona 4 Golden lol. But it's not beause of the tropes...it's because as a game they are either boring, broken, or just meeeeeh. They need to fix that part. Making the gameplay part fun, not grindy, and not take hours to start...then maybe they will hit more people..
but they will never return to the 16bit days. The market just isn't interested in that style anymore and chasing after them, will end up in steralizing what made them different.