As an end-game raid leader it is extremely important to have addons that measure healing, damage taken, damage done, how people died, etc. without them you cant see who is making mistakes in a large raid setting when it isnt obvious and yes , playing your class subpar in a raid setting is a mistake.

Some people enjoy competing for server, region, and world firsts in MMO end game raiding. The low level world bosses I agree nobody cares about. But I dont see how hardcore raiders spending hours a night trying to compete with other guilds doesnt warrant a server first achievement. I dont see the issue with that except it makes the more casual players "angry" for whatever reason.