This is essentially the crux of it. There are more than enough capable graphical artists and composers out there to keep wage costs down when producing the next big AAA title, but wRPGs need actual game design finesse and require a significant investment of manhours to balance and tweak. Good game designers are a rarity, especially when you're designing something that makes use of emergent functionality. Proper open-ended wRPGs that are almost sandbox-like in their freedom require vision, creative freedom and generous scope in terms of deadlines. Essentially, they're the stuff of nightmares for shareholders and CEOs who want everything micromanaged in terms of budget and deadlines.

Games like PoE, Wasteland 2, Divinity: Original Sin were successful by wRPG standards, but nowhere near to the level that AAA investment would require.

JRPGs are defined by their simpler mechanics and more strongly defined narrative. Again, these are much easier to balance and tweak than a true wRPG whose gameplay tends to be a lot more open-ended. Action wRPGs offer something much closer to the "open-ended" style of classical wRPGs.

If anything, I'm glad that JRPGs are starting to adopt some wRPG features now. The genre was starting to get a bit stale, although the Tales series is always there for JRPG traditionalists. Final Fantasy 15 took a major leaf out of Witcher 3's book, and Zelda: Breath of the Wild had some astonishingly clever quest design of the kind that you would ordinarily only find in core wRPGs (as in, you actually had to read, explore and study).