Zelda II can be considered an action RPG...other than that, I don't think so.

I wouldn't say it's more complicated to define them now than it was in the old days...it's just that there are quite a few games these days, especially AAA, that flirt with some of RPG mechanics and are sometimes mislabelled as (action) RPGs, while actually still being action-adventures or shooters in their core.

Does 13 sentinals Aegis Rim count as a JRPG is what I wanna know. And for that matter is Horizon forbidden west actually an RPG or is it an open world game with more nuance.

Can't say about Aegis Rim, but Horizon is good example of this breed of modern games that are action-adventures that flirt with RPG mechanisms (so, quasi-RPG, or maybe RPG-lite). Personally, Witcher 3 has become my go to example of the game that sits on the border between proper action-RPG and quasi action-RPG, so it's easy to determine, by comparing some game to it, which side of the border said game sits on.

Being open world doesn't really matter in determining whether or not a game is an RPG.

I think a RPG is any game where you have to level up the character. 

Tim Cain's 1999 presentation about RPGs that he made for GDC 1999, but never got around presenting it, presented now on his channel like it was 1999 (cue in Prince's 1999)