You uh... might wanna go play the game, my dude.
If memory serves, the Re[in]carnation side of the crossover involved extensive input from FFXIV's writers. In any case, it's considered reliable insofar as the information it provided about things in FFXIV are concerned.
Yoko Taro's team probably had more creative control over the NieR raids in FFXIV, ironically.
Different interpretations and values notwithstanding, I believe part of the disconnect stems from some people, myself included, thinking more deeply about the story than what the devs accounted for. In fact, I believe Yoshi-P even said as much at one point. It's not even really about Venat for a lot of the naysayers. It's more about how poorly things stand up to scrutiny. It's in human nature to value that which is shown over that which is told. For my part, I look at the story, specifically Venat's part in it for the sake of our discussion here, and I see a character that wasn't selfless or pure. I see a character that unilaterally decided on a course of action for an entire world and its inhabitants based on information about the future gained from a time traveler. A character so headstrong as to believe her way was the only way, and she confirmed this for herself by subjecting her people to a test they had no chance of passing without the information she withheld. This? This I'm fine with. Sometimes people are like that. I am not bothered by Venat's nature or even the actions she took. The story is what it is.
The problem I have is with how the narrative frames it. Wiping out all life on a planet, whether well-intentioned or not, is pretty messed up in just about any conceivable sense. It makes sense a lot of characters wouldn't get overly bent out of shape about something that really didn't affect them - we see this play out with people IRL all the time, not being moved by ancient, or even comparatively recent, events that had nothing to do with them. So this is also fine. I find it odd the Scions weren't even slightly bothered by it, but so be it. That's how people roll. What I found myself unable to reconcile specifically with Venat wasn't even Venat herself. We're told we should feel X way about the character and the events surrounding it, but what I saw in the game left me with a very different perception. If you want me to think something was an absolute necessity, then show me that. Don't tell me it and show me a bunch of stuff that'll turn it on its head under even cursory scrutiny.
Like I said, Venat as a character is fine. Her part in the narrative would've worked fine for me with better framing and more showing than telling. I'm well aware the majority disagree with this take, but I kinda don't care. It's my take, and while I am open to having my mind changed, I've yet to see anything that would.
As for people spending a year fighting it out, I might note that most people tend to react very poorly when someone tries to tell them their opinion, whether well-founded or not, is stupid. Not just wrong - stupid. The more you try to tell people they're stupid, a bad person, etc. for having a dissenting opinion, the more they will dig their heels in and keep defending their position. This is doubly true if it's about something they care about. FFXIV is something a lot of us have dumped far too much time and money into. It's something many of us used to thoroughly enjoy. People that care about something will want to be outspoken when they feel it's being harmed, or in the case of a game going in a direction they perceive as bad for its health.
As for me, I've already given up on the game at this point. I know the direction it's going in won't change, and I'm aware I am no longer its target demographic. I really only hang around because I'm keeping some friends' estates from getting demolished while they are off serving, and for the most part I only poke my head in these debates because I am bored out of my mind at work. :P Otherwise, I just comment in suggestion threads and the like in the vain hope at least some measure of the game I used to enjoy so thoroughly can be brought back.