CG of the monsters, acting, directing/staging of scenes as well as the action/fighting were great however they have transformed the original webtoon story - a psychological thriller about people giving in to their desires and becoming monsters related to said desires - into a few very simplistic man vs monsters fights and then a lot of men vs government/army situation. As a fan of the webtoon's more in-depth take on the psychological side of the story and the internal conflicts of each character, the Netflix adaptation's omission of those elements was quite disappointing.
And so by ignoring the basis on how people turn into monsters based on desires, the story becomes quite inconsistent with how and when people show symptoms of turning and when they become monsters. Characters who were explicitly showed initial symptoms of turning stayed fine til the end of the season and that fact just got brushed off. The monsters that people turn into would also not make sense without prior reading of the webtoon.
Viewers who don't have prior knowledge of the webtoon it is based on may enjoy it a lot more as other components of the story are quite good. However, the inconsistencies stood out to me personally and ruined my experience to an extent.