Correct on all accounts.
It was a faction to which both the Kingdoms of Lordaeron and Stormwind were united as members of, along with many other nations.
A faction that still exists today, albeit now without Lordaeron.
You will take what I said to mean something entirely different though.
The assumptions are all mentioned clearly here Amirdrassil has left the Dream - #133 by Darielle-proudmoore
As Highlord of the Ebon Blade (until he stepped down), he no longer does. During the earlier events of WoW, or the events between the Frozen Throne and WoW, which is the a time period relevant to what you were discussing, is a different story.
I’m not making any claim on who “owns” Undercity. The canon of this game establishes that Undercity was disputed in ownership at the time this game released. The canon of this game also establishes that there is no new or old Alliance. One evidence that I’ve cited is in Wolfheart, which occurs around the start of Cataclysm, where Genn Greymane is explicitly petitioning to rejoin the Alliance, and the effort of his petition is that he has to account for betraying/abandoning the Alliance. Do you understand what the word “rejoin” means?
The majority dying is not an assumption. I even linked the lore earlier.
The whole discussion that started with someone else was about that.
Alliance of Lordaeron is literally called the Old Alliance, holy 
lol
The Alliance of Lordaeron (aka Lordaeron Alliance ,[1] Great Alliance ,[2] Grand Alliance ,[3] Human Alliance ,[4] Alliance [5], or old Alliance )
This is the blizzardwatch article that you linked. It is not, itself, canon, but an article on an external third-party website. Even in that page, the word “majority” is never used. The part you bolded was “With Terenas gone, the kingdom fell into chaos. Unimpeded, the Scourge proceeded to wipe out what remained of Lordaeron.”. That also does not claim how many people escaped, or what portion of previous residents either died, or were raised as Scourge.
Bear in mind of course, that this is the one assumption I said was probably actually true, and went forward with by assuming that 80% of Lordaeron’s population directly became Scourge. That then lead to several other assumptions being made. You might want to read ahead in my post rather than shutting off your brain the moment you see the word “majority”.
You’re linking to Wowpedia, which is an external resource, and is not canon. It’s also now a deprecated website, although that’s understandable since it happened recently, https://warcraft.wiki.gg/wiki/Warcraft_Wiki is the “new” one which is being kept up-to-date. Note that the words “old Alliance” do not even have a citation that references the phrase being used anywhere in any actual canon source.
Come on, you have to be smarter than this.
What does wipe out what remained of Lordaeron mean to you?
Blizz operates in numbers of 80-90% for elimination numbers (Elves and Draenei) so that can be assumed. I am not assuming numbers. Just saying that it was a majority. Because it was enough for the kingdom to fall. And Blizz Watch, not Blizz Planet is pretty accurate with their lore.
JFC, all of these are trusted source of lore. Just stop. I’m putting you on ignore because it’s obvious you are just trolling here.
It could mean one of several things. For example, if most of the residents of Lordaeron escaped, “what remained of Lordaeron” could mean the minority that remained. It could be completely ignoring the people itself, and referencing the Kingdom as a whole, as in the infrastructure, etc. Or it could mean most of the people. The phase “what remained of Lordaeron” does not automagically translate to “the majority of people”.
Woah, [citation required]
Third party libraries and articles are no more “trusted” of lore than Wikipedia is a valid citation (it never is). “Pretty accurate” is not a standard, and doesn’t even mean anything, especially since it implies room for inaccuracy.
It means it left the Emerald Dream. General chat was too toxic, even for a World Tree.