I would always argue that we should have a Need Before Greed loot system in all instances.
People asked for personal loot because back then, some people would roll need on everything and there was a big fuss if someone was seen as a “Ninja looter”.
With the “personal loot” system, all items looted have a light blue text which says “you may trade this item to those who were also eligible to loot it!”
Which means, the personal loot system is affectively “AUTO Ninja”.
When someone gets loot from the auto ninja looting system, which you need, and they just leave the dungeon and say they would rather keep it for an off-spec which they never use or for disenchanting because they love gold… is that in any way fair?
The new Need Before Greed looting system has been updated - it isn’t the old Need Before Greed system it used to be - so if someone already has an item in that slot of higher item level than the available loot, then they cannot click Need. Also, if a profession pattern drops - only those who have the required profession may roll Need.
In my guild raids, I have always insisted that if someone needs something, they should click need. For off-spec they should roll greed. Nobody ever Ninja looted in my guild raids.
Everyone is eligible for the loot that drops. Everyone put in effort to be there. If they died or pressed less buttons or needed extra practice on tactics, doesn’t matter. Need Before Greed is the only fair and equal looting system that the game has to offer.
If blizzard made duplicates of all items available to everyone who might need it, as you seem to suggest that they should… it would break the game. People would make groups of all cloth wearers and gear up all the cloth wearers from their guild in 1 raid. Likewise for other armour types.
Your suggestion would cause more issues than it would fix.
In my opinion, they should add the Need Before Greed system to Mythic+ Dungeons too.