You are wrong. Sociopaths can feel love. Even psychopaths can feel love. Sociopathy and psychopathy function on a scale/spectrum, and some psychopaths and some sociopaths do feel love. Do feel attachment. Do get attached. Do feel affection. There were actual interviews with people diagnosed with sociopathy or psychopathy and a number of them have confirmed that they did feel love, affection and attachment towards their partners or friends or family. And they do definitely understand it, even the ones who do not feel it, they can understand it as it is perceived/felt/described by others and they even feel regretful that they themselves cannot feel it. But again, sociopathy and psychopathy function on a spectrum. Not all psychopaths and not all sociopaths feel and act and think the same, some cannot feel love, but some can feel love. It is wrong to generalise. In the case of Zenos, we do not even know for certain whether he is a sociopath or a psychopath and even if he were, we do not know where on that scale he would fall. And we do not know these things because he is not properly developed.
And when I call for Zenos to be brought back, I don't want him to come back and again do nothing. I never wanted that for him, to do nothing, have no development. I always wanted him to have development, especially now when the main story is done and other characters could be developed more/properly.
I don't want Zenos to be brought back to undermine death. That is not the reason why I want him back. I want him back because I have many unanswered questions that I want answered with him alive and involved in the story and because I want him to be developed properly. If he had been developed properly back in Stormblood or Shadowbringers or even now in Endwalker, and then killed in a meaningful way, I would have been okay with that and I wouldn't have wanted him back. I just hate seeing wasted potential, having way too many unanswered questions, and so on. If my concerns had been addressed from the start, years ago, I would not be writing any of this now and I would have been perfectly happy and excited to move on to new villains.