Astral starts slow, frankly the first two hours is meh and had me worried. But it does get going and is quite something special.
I felt the same way. The game does not really start until File 3, and man does it really take off. Overall it sits right next for Fire Emblem for my top GotY contenders so far.
Anything before chapter 3 seems like world and character building as well as a steady introduction of gameplay mechanics. While worrisome at first, I feel that is the way to go with this game overall as the combat system does have a lot put into it, and some players may have been overwhelmed otherwise. So yeah, I was worried too. But in retrospect I can appreciate how they started the game out overall.