The addons never done the job for you. You still HAVE TO pay attention or you die DBM or not.
As for other addons, they just help with visibility and improvements that many ppl including me love to play with like elvui.
Weak auras is a great way to put important information on the middle of my screen.
I could in theory ofc put my whole action bar there but that would make it a bit annoying wouldnt it.
Currently my weak auras mostly only appear when im in combat so they dont take up my screen space.
For another example i could say base raid frames for a healer, especially for a resto druid is pretty much unusable. It only shows 3 buffs at any time, when you will have way more than 3 hots up on certain raid members at any one point.
Sure if blizzard will bother to do some improvements maybe it would stop that many ppl from using addons.
Addond are not inaccessible to anyone. Everyone will be once new to the game and someone else will just tell them about it if they dont read of it on their own. Thats how it happened to me and with everyone else in the history of wow who has played the game at any point.
I could also argue that having addons wont make you magically do hard content and that ppl who do use addons doesnt mean they would be bad without them.
Bad ppl can die in bad even with addons working and good ppl can play with almost no addons or nothing at all.