Eeh, it's kinda not what I expected. Trailer makes the game look more intense and harder than it actually is, with a bunch of cool air combat, that you rarely do. Could be because I was playing on normal difficulty, but the game won't let me play on higher difficulty anyways until I S-rank some missions.
And that brings me to the typical annoying Japanese design stuff: How do you S-rank missions? By not using the healing items the game gives you. Why even have those then? You also need to complete the missions under a required time, but you don't have dps for that until you get end-game gear, so the game basically wants you to do the same Normal level milk-run missions twice in order to be able to play higher difficulty. No thanks, that's just boring grind - and I say this as the guy who suffered through Hell&Hell mode in DMC5 for the "All S" achievement. I'm just tired of this design, just make the game have proper difficulty, please.
Surprisingly, the game also has multiplayer, which I legit didn't even know until I fired the game up for the first time. I tried matchmaking on a Sunday night, got a match in 10 seconds, but I'm pretty sure I was just playing against bots.
EDIT: Completed the campaign, it does get better in second half at least. Completing unlocks the "Simulation" wave defense mode, where you use any of the NPC mechas and weapons after unlocking them. Has its own tech tree where you keep unlocking new stuff. It's so freakin' massive it's almost like this is the game's real main gamemode, so the game definitely does NOT lack content.