I mean, I didn't go from that to this at all, as both are independent points.
You
are holding your guild and your group back by having the BIS Legendary, and aren't trying to stay ahead of the curve of the AP grind.
That's like saying that "Oh, only 1% should care if your raiders show up without enchants or without fully upgraded gear", which would be a ridiculous claim to make.
No weapon drop or trinket drop had as big of a % difference in terms of one item slot. If you have roughly the same ilvl, but one player has two BIS trinkets, and the other one has shit trinkets, the DPS wouldn't be as big as the difference between the BIS Legendary and the worst legendary, especially because all the utility legendaries were garbage at the start of Legion.
That's just revisionist BS. The majority of players hated the system because it was needlessly punishing and you literally couldn't get more than three legendaries for the longest time. Not being able to get the best legendary for your spec until like 7.2/7.3 because you just didn't get lucky and permanently being gimped because someone else got luckier at the start of the expansion is a fucking terrible feeling for an RPG, and yes, that was a thing that was possible.
Here's an image of someone tracking his legendary drops, for example.
Yes, it was. Generally for most specs it was at least a 15% DPS difference.