IMHO, Symbaroum's biggest sin for me is that it hides some pretty major game lore in adventure paths that feel a bit like novels that the creator may have wanted to write. The primary AP is basically the metaplot of the setting. Regardless of how creative the setting may be, I don't necessarily like APs like that or when setting designers do this sort of thing. But I also generally prefer settings that are created with intentional space for gaming groups to come up with their own answers to setting mysteries and questions.
Back in the early 00s, the same people who are making Symbaroum made a Swedish game that's sort of a cousin to Mutant Year Zero called Mutant: Undergångens Arvtagare (Mutant: Heirs of the Apocalypse) that used a similar model, with a series of geographical sourcebooks combined with an adventure path that would eventually reveal some major things about the setting and make some pretty big changes. While I'm generally against metaplot, I don't really have a problem with this kind of thing, but one should be aware that it means that the game/setting is essentially built around this one campaign. In this sense, it is sort of like a Bioware-style CRPG, like Dragon Age or Mass Effect. Once it's done, it's time to look around for something else to play.
This is unlike "traditional" adventure paths like Paizo does, or big campaign adventures like Wizards does, who generally are either about eliminating a threat to the status quo or at best making changes to a highly limited region. This is a necessity, because the companies in question intend to keep making stuff for those games/settings forever.
I think it's cool that the market has room for both types of campaign adventures, and they have different strengths and weaknesses. Big change campaigns let players actually have an impact on the world, but then leave it behind. Status quo defense/restoration let you come back to the world with new PCs who get to do something different, but whatever the first group did has probably been forgotten.
I also take some exception to the use of the term "metaplot" here. My understanding of metaplot is that it's something that happens
outside the game. Something like "Tethyr used to be torn by civil war between a number of factions following the murder of the royal family about 20 years ago, but now the rightful heir has returned and united the country in a novel trilogy." If it's a thing the PCs do in their adventures, that's just plot.
