Yes, I do wonder why Ishikawa didn't do much with Zenos, but I choose to hope and I still want her to bring him back and do a lot more with him. He is not even the only character that wasn't developed much. I can name a few of them, such as Lahabrea, Elidibus, Varis even, Emperor Xande, the remaining Ascians, Unukalhai, Cylva, etc. I have many questions about all these characters and about other characters as well and I'd like to see them developed as well.
I did not reduce Emet-Selch to a sociopath, I said he could have come across like that but thankfully Ishikawa developed him and gave him depth, gave him a backstory and reasons.
I am not making excuses for Zenos because of his childhood, but I am saying that his childhood and life in general did contribute to his personality. Again, monsters are made, not born. No, it doesn't excuse him, but it should make him more understandable.
Emet-Selch is one of my favourite characters if not my number one favourite character in FFXIV and I loved what Ishikawa did with him. I just wish she did something similar with Zenos, as in: give him depth, give him a proper backstory. No, it doesn't need to be a grand reason or scheme like Emet-Selch's desire to restore his world and people, but it should be a proper story, with in-depth development. That's what I want.