I don't think they can let the Elemental Weaknesses system active in a scenario where only monsters can use one of the 6 elements, which brings us back to the hypothesys of them removing the system completely.

It's not much about of other forms of healing existing with different element, they've been there for quite a lot of games.
It was more about the typical FF-esque spell called "Cure" being light-alligned.
But since the two spells Conjurer will get will probably be called in a different way, I guess you do have a point in the end.
I don't think leaving fixed tiers and typical FF-esque names for spells is the only way to mantain and nourish an FF-esque atmosphere in the game, I totally don't think that's *necessary*.
But still it was one of the many aspects contributing to that goal.
While I'm not claiming the game has got to suck if those are not there (that would be very short-sighted and childish), I can't say I'm happy either.

I'm 100% sure Yoshi-P's team can mantain the FF-esque through other means, but still, if they could have kept ALSO those aspects, it would have been even better for me

We'll all learn to live through and forget about it, but I still am not happy this is happening.