Thats a narrative choice though isn’t it? The writers can choose to re-diverge back to this original narrative.
DF might have given us closer relations between the two factions but it doesn’t change the Forsaken have been distrusted since before Classic and have, honestly, only given the world more reason to distrust them. The general unease with the Forsaken in Classic is a great start, even played out as neutral with the Horde as opposed to friendly. BC helped mend relationships as they helped with the elves, only to destroy that trust by strong arming them into the Northrend campaign. Not to mention the Wrathgate which put UC under Kor’kron occupation. Varian was ready to retake the city for the Alliance. Cata, albeit on the orders of Garrosh, gave us Gilneas and Hillsbrad. WPL seems to be a solely Forsaken plan, but doesnt change the fact Sylvanas kidnapped Koltra (although given the circumstances I suppose she was technically allowed to). They were taking and enslaving Pandaren when the Alliance meets them in MoP. The Ebon Blade have attacked the Forsaken twice (1.5 if you don’t really count Arathi). Theres the whole Stormhiem questline that flows into BFA.
And thats just the broad overview and summation of the Forsaken’s less than trustworthy deeds. Thats one expansion against seven characterizes them as underhanded, seedy, up to no good, violent, distrustful.
Like I said,
And thats not to say there can’t be cooperation or coordination between the Forsaken and the living, or the Alliance. We’re not looking to take over the world or eradicate every inch of humanity throughout whats left Lordearon. The Argents still exist don’t need to be destroyed (though I have my own gripes about their control of EPL being a barrier to the Forsaken and Blood Elves), the Gilneas/Lordearon border can be diplomatically addressed, Southshore can be given an order of protection/promise we wont blow it up again, and they can discuss the Lordearon/Arathi border. These are all important diplomatic questions that need to be answered with cooperation. However, as stated elsewhere the Forsaken need to showcase what the Forsaken are at their core in a world that shouldn’t trust them and actively encroaches on their borders, questioning their right to exist.
A very speak softly and carry a big stick diplomacy