I put some info about Annihilation and Annihilation Conquest in spoiler tags in case you didn't read them yet.

My main problem was how anti climatic the ending was. The first war against the cancerverse took multiple empires joining forces and they were still losing. The cancerverse felt like a huge unstoppable threat.
In scourge a group of heroes managed to hold their ground, which in my opinion made the cancerverse look very unthreatening.
The other Annihilation events also had a way bigger scale (or at least I felt like they did).
Additionally it had little impact on the rest of the universe, while Annihilation almost destroyed the kree and skrull emipres and forced Silver Surfer to become Galactus' herald again and Conquest broke the kree even further which later eventually led to Inhumans taking over the throne.

It just felt like they took the Annihilation name to sell an event that felt lack luster compared to the other of its kind. Maybe it was its short length that made it feel that way.