You people and your absolutes. 
And those people aren’t the entirety of the WoW community or every single progression player. I can’t help it if you don’t understand what savants at this game are like. They do exist. Not everyone needs addons. Most, some, sure.
What do you want me to do, track them down and follow them around with a camera in game? 
Saying 100% of players around the world must absolutely use addons is simply false— we don’t know everyone and no one should be dealing in absolutes.
Should some or most be using addons? Sure. But people need to stop saying all have to, when we don’t know all.
That was never the argument. Your argument was that some people could play at 100% doing high end content (like the op is trying to do) w/o them. The reality is every single top end player in the world first race is using them. So where is your proof otherwise?
There is a bit of context probably missing. Normal and Heroic dungeons, yeah. But when you start getting into Mythics, where timers may be more critical, I could see people getting more picky about addons.
This has been a problem for quite awhile. Big part of why I dont’ bother raiding anymore is I refuse to use voice chat. I want to listen to the game not a bunch of people banter. Only addon’s I use are recount and tomtom. I just like recount so I can see how I am doing not to spam groups or call anybody out. Just started using tomtom with 8.2 to help with rep grind for pathfinder part 2.
It was always my argument. Other people started making it pointedly specific, not me. We cannot say 100% of the millions of people who play across the entire world absolutely need addons to do their best. And this whole “prove to me people can play at their best without addons” is just silly and I already told you why it was.
As I keep saying… most need addons to be their best? Sure. We can say that. Absolutely.
The only people who wouldn’t aren’t doing content or are just really bad. Especially since this is all really about the OP.