Dropped both the anime and manga when trying to view either due to it seeming pretty pretentious in it's presentation. The series' premise seemed to be promising for a Shonen, though whatever positives it had in it's appearance as a series in which anyone could die and where strategy and tactics would be needed to win battles were thrown out about 5 episodes in, where it became clear after the protagonist's plot hax that Giant on Giant battles would be the main source of the heroes' victories and the protag's plot armour was as thick as Naruto's.
The characterisation was very weak as well. Other than Jean, the main cast were very stereotypical archetypes that went through little development.
Doesn't help that the anime series Blue Gender had a very similar premise of humanity trying to survive against a monstrous threat and executed the concept far better, mainly due to not relying on Battle Shonen tropes to help the heroes through.
The anime's useful for normies and casuals as a gateway anime. Other than that, there's no point viewing it when each aspect of it has been pulled off better somewhere else.