I believe the last quest that felt relevant to the plot was 'A New Dawn', right at the end of the Stormsong Valley questline

I've begun to do any and all side quests I can find in Kul Tiras, recently doing the storyline in Falconhurst, which netted me an achievement that seemed like it was finally heading the way of actually continuing the story with Jaina and co. Trying to Google what to do next is almost impossible, not knowing exactly what quest I did last and references to stuff I have no clue about. Did all the story quests for those zones too (Nazmir, Zuldazar, Vol'Dun) and yet still there doesn't seem to be any way to progress the story in Kul Tiras. I thought it was quite the whiplash in terms of story, seemingly completely abandoning Kul Tiras but I carried on anyway. I asked in Newcomer Chat about what the next steps were, and was directed to the alliance war quests on the nearby boat. Taelia and the rest of the crew having nothing else to say or do. However, it seems like the storyline just completely drops off there. I have completed each dungeon related to those zones, in what felt like a pretty conclusive end to their respective arcs.

Currently I'm questing around Kul Tiras, after what I assumed was the end of each three zones stories (Tiragarde Sound, Drustvar, and Stormsong Valley). I get even more confused than I was before. I'm finding it very difficult to follow the storyline, and every time I ask in Newcomer Chat or even just Google it. At the time of writing, I'm currently level 45. Assuming it's Battle of Azeroth based on achievements and such, but I've never been told it explicitly. Pretty much just following what appeared to be the main questline. Hey, I just picked up the game a couple days ago.

Wow tiraguard sound story tracker