The current story in Battle for Azeroth is like that: the armies of the Alliance and the Horde have been depleted. Very few warriors remain. Anduin said in the latest cinematic, that they’re “so few” and he can provide an army just for one final assault. Varok Saurfang’s sacrifice has a meaning - a second Siege of Orgrimmar which would lead to heavy casualities now isn’t needed and both the armies can relax for time being.
The depletion of the armies is a serious problem for a continuous game like World of Warcraft, serving us different expansions which offer a war after another war. Historically, we’ve looked for allies - whether they’re the jinyu, the pandaren, draenei and orc from an alternative timeline, and later all kind of allied races - zandalari trolls, kul tiran humans, nightborne elves, lightforged draenei, etc etc etc…
But what we truly need right now is a time gap. Four years have passed between the events in Warcraft 3 and World of Warcraft. For the story to continue in a meaningful way, it would be good if there’s a large time gap, in which the Alliance and the Horde (or perhaps, a non-faction consisting of all races) exist peacefully. Perhaps for 20-30 years. Let them rebuild, let them raise children and new warriors.
And when the next expansion begins, let it start at least 20 years into the future.