Food for thought.
Hypothetically, primary stat is king, so much so that any item that is higher iLvl is better, regardless of whatever else is on the item.
Player STILL want optimal secondary stats. There is STILL going to be an item that is better than another of equal iLvl.
Let's say Guild A is raiding. They have a Shadow Priest and a Demonology Warlock. Let's say hypothetically the Shadow Priest wants Haste as their main secondary stat, the Demonology Warlock wants Mastery.
Both have iLvl 200 bracers. They approach the raid, bracers drop for the Shadow Priest, 205 iLvl, they're loaded with secondary stats like, 60% mastery, 40% crit. Next boss (because more than one of each armor/slot drops per raid), bracers drop for the Warlock, 205 iLvl, they're loaded with second stats like, 60% haste, 40% crit. Now what? They both have items that are upgrades, but more than likely feel bad about the quality of life of not getting the stats they want.
Also, why would you pass on an upgrade that you won? Because it's better for someone else, when you're in a guild and you're working on that next boss why would you not want to give another player an item if it's better for them than yourself. Why would you take bracers that are 500 DPS increase for you, but 800 DPS increase for the Shadow Priest?
A lot of people feel that split running is solved by having no tier and iLvl being king but it doesn't solve it.
What about trinkets? What about the Agility trinket that procs Nature damage? The one that scales ridiculously with Enhance mastery, the one that the Rogue for example couldn't care less about? What happens when the Rogue gets it and can't use it, vs the Shaman that can, and wants it, and massively gets improved because of it?
What about the caster trinket that procs Shadow damage and scales with Warlock/Shadow Priest modifiers, but actually ends up being looted by the Mages that don't want it?
In Nighthold Convergence of Fates had a different proc rate for each user, so you wanted it on those that took the biggest advantage of the hidden proc rate (For example Retribution Paladins in Nighthold), what about situations like this?
Guilds are borderline organizations, being part of a guild involves working as a team, making an individual sacrifice for another players benefit that improves the entire guild as a whole. Removing any influence on how gear is distributed just undermines what a guild is supposed to be.