I think with animation you can have at least some basic objective standards, even though the actual implementation is a matter of taste. Pixar films (which I don't tend to like) look incredible. Love*Com (which I think is amazing) looks wobbly. I'm reasonably confident that unbiased animation professionals would see YOI and consider it decently animated, even if they might not like the designs or the inbetweens (...). Also, I think that people who consider it badly animated need to be forced to watch the whole of Violinist of Hameln back to back then come back with a new appreciation of the painstaking effort the animators put into this skating show because it's jawdroppingly awesome to look at as television anime goes.
Likewise with audio. I hate jazz and piano music in general, for example, but if a piece of music was professionally produced and has fans then I don't think it's reasonable to say it's ineligible for recognition in awards just because it doesn't sound as good to me as dodgy European 90s pop. The YOI soundtrack was regularly trending online as music fans, skating fans and anime fans came together and enjoyed it. And the soundtrack wasn't just good; it was actively worked into the very fabric of the show, with musical flourishes in the skating themes thematically tied to events that took place in the story. That's unusual and, in my personal opinion, worthy of recognition on its own.
(Incidentally I'm a fan of the animation in YOI but I'm not especially biased towards the music. I didn't even buy the OST myself because it's classy and I spent my anime CD budget on other, less classy shows. I think it's objectively good because it's met with quantifiable mainstream success more than that I particularly like J.J.'s annoying theme song.)
Unfortunately Kabaneri has the issue of the separate $99 paywall blocking the majority of legal viewers from ever seeing it. I think it would have been a lot bigger than it was in the west if more people had been watching. I'd have loved to see it myself, but if they want me to cough up for Prime to do so then I'm afraid there's other anime out there.
Absolutely agree that the nominations should have incorporated more diversity in general, though. YOI probably was anime of the year in terms of its impact regardless, but Crunchyroll fanned the flames by putting it up in so many categories in the first place, especially against weaker contenders which would obviously get steamrolled.
R