Theres nothing wrong with complex shooters, but generally once you get over a certain number of buttons the fun factor drops. Of course that also depends on what the buttons are for.
Like you don't want this super complex FPS where you have a button for kick, grab, pull, reload, move(x4), fly, jump, crouch, prone, lean left, lean right, grenade, mine...blah blah where you need all of those at any given moment. However many of those can still be in a game as long as they arent a requirement for every battle. Like (my fave example) Tribes. Mines and grenades were there. Grenades I put somewhere close to throw in a fight, but mines were on a less used key because I only dropped them to trap an area. I also had 10 keys dedicated to different equipment loadouts...but I only needed those when I wanted to change my loadout. I wasnt constantly reaching for them.
So thats where a keyboard is nice. It allows for advanced functions in game, but doesn't mean playing it becomes more complex.
Analog stick...for headshots? Surely you jest.