I think it kinda depends on how you define good.
Remember that 10 years ago people were doing alot of this stuff for the first time and had to figure these things out by themselves. Alot also had the illusion that gear meant all. As many have said, we are on 1 patch talent wise. We can work towards one patch. Where in vanilla all this stuff was constantly in motion.
Alot of you are forgetting that you are standing atop these peoples shoulders. You are using the information, tricks etc they found.
Like others said, 2005 there were no streams, not alot of high quality movies etc. Even Blizzard themselves were constantly finetuning.
When i started raiding in vanilla (Pre-ZG release) i was even under the impression that people would avoid reading guides to make the dungeons more challanging and epic (was laughed at hard in guild chat).
Just because we know that an apple falls to the ground when falling from a tree due to gravity doesn't make Newton a fucking dumbass all of a sudden.