Blizzard did address it, they stated their engine cannot withstand mega server infrastructure, it cant hold up the modifications required.
This is because allthoough they canupdate it they cant make the servers cores larger or overclock it further to wothhold larger storage in each individual core that its run on.
This isnt blizzards fault.
This is a industry problem, when the same games are leading the market for 2 decades, im afraid the games end up too old, the f2p demand from players drove the genre into a hole regarding new launchs and killed off every title that attempted it.
But at the same time games were frequented by plauers boycotting til it went f2p. WoW and FFXIV were the only surviving sub based games which had communities that stuck it through and when it went sour the players who tried fighting for returned to sub.
This ment these games survived.
WoW is 10 years too old, and without taking the entire game down for 2 weeks to remove the engine and redo the games coding onto a new one to replace it there isnt a fix.
Everquest tried taking its game down to do exactly this as theres caught fire when pushing it too far, it went down for 3 weeks, the games playerbase never returned and the game died.
I dont blame blizzard for not taking that risk.
The only fix, is WoW 2 which i do think will come, in the same form as overwatch do it, they will recode it on the side lines, merge the player accounts into it and auto upgrade without chsrging the players a 2nd time around or forcing everyone to restart.
But thats not a fast process, performing that sorta tech in a mmorpg is very different to overwatch so if they are doing it its not releasing at any speed.
As they said theres major changes to WoW coming for the following expansion time, and this could be it.