I think I stuck it out for linger than you did, but I had basically the same reaction and for the same reasons.
Besides the primary author going so hard on violence as the solution to every problem, which made things awful repetitive after a while, I think he was stuck on the classic misconception of evolution as progression.
In a setting where Earth is a "deathworld" and most habitable planets have or more factors that makes them "easier" for complex biological life (lower gravity, weaker seasonal variation, less tectonically active, less aggressive microbiome, etc) humans, being well-adapted to the conditions here on Earth, are poorly adapted to the conditions on the "easier" planets. Which means there's no inherent biological reason for humans to be an existential threat to intelligent inhabitants of the "easier" planets.
For a while, it seemed like the overarching plot would be about that. Why did the V'Straki go all colonial-imperialist despite being ill-adapted to the worlds they were conquering? Why did the Hierarchy misunderstand this as an inherent characteristic of deathworld-derived sapients in general? Why did they think that the only way to deal with this was not only to wipe out all deathworld sapience, but to take secret control of all other intelligent civilizations and periodically wipe them out too? And sure, humans may be better soldiers than the average galactic, due to bitter intramural experience, but what happens when we come up against problems that can't be solved with dakka?
I wanted to read that story, not the story the author wound up writing.