Alas, this is as far as variety goes. The missions are so similar that they could easily merge into one were it not for the nice quiet hours you get to enjoy while the cutscenes are on. The trouble with space is there’s no ground, and thus no ground targets to deal with. It denies developers a lot of extra options to mix things up. It’s always “kill this squadron” or “defend this whazit,” and they all amount to the same sequence of events - fly, shoot, rearm, shoot more.
Shooting things is fun; shooting things with a custom set of weapons even more so, but three hours in and you’re still shooting the same baddies in the same formations and chasing the same elite squadrons around in circles. Sylpheed is never bad; it just never offers anything fresh.