Its a Shooter, an FPS Shooter. So yes its about combat. When theres something you do 90% of the game, then the game is pretty much about that. I dont think you're customizing your weapons 90% of the game? Customizing guns isnt something new either, and you're just coming off as a dick to think that we're all not liking this game THAT HARD just because you can customize your weapons.
And its not like you could customize them a lot either.
I was playing the PC version, and to me it felt like an console game where the aiming and shooting of guns was very weird and that it was a step backwards in terms of SHOOTING A GUN IN A SHOOTER. So i grew bored and stopped playing.