I think the point is that you're playing yourself, not a character in the 1940's. If you get good at throwing grenades, then you'll be good at throwing grenades. I'd imagine people are also better at firing from the hip than it seems in the game but I wouldn't ask for a crosshair icon to know where I'm aiming. Sure, it'd help, but the game is meant to be hard.
I'd love to be able to toss a grenade through a window when trying to defend a CP, but I'll have to just keep practicing until I get good at it!