Well, I have not read the book myself, but taking all of this at face value and lacking context, consider the following.
Massive World War Between Alliance and Horde, intense fighting in all corners of the world for 4 years. (Cata-Mop)
Invasion from an Alternate timeline, the likes of which Azeroth had never seen since the First and Second War, resulting in a massive interdimensional Campaign of Conquest on an alien planet lasting 2 years. (WoD)
The Largest Demonic invasion in history since the War of the Ancients, resulting in intense fighting on a global scale. Resulting in yet another interdimensional Campaign of Conquest on an alien planet. One far more unforgiving than the last. That was an entire year.
The Battle for Azeroth. A War that resulted in the genocide of the Night Elves. Their Home and the home of the Forsaken was scorched and blighted. Bloody conflicts erupted in every corner of the planet. The Zandalari (Which is just a small Island nation, it’s power mostly derived from cultural, political and religious significance) had a massive civil war against the Blood Trolls, Ghuun, and agents of the Old Gods. Kul Trias has a Civil War against the Coven and the Tidesages. The Naga took sieged the advantage to free an Old God, the first unshackled Old God seen since Primordial Azeroth. It is still unclear how long this went on, but precedent says at least 1 year if not several.
All of this happened in less than a decade. So, can the forces of Azeroth really put forward any massive armies at this point?