I have no idea how Sam got his powers in the comics, he's not a character I ever really got into before.
And I do prefer characters to have unique abilities and skills, but I think MCU Sam has that. At least to a degree. Granted, his individual abilities aren't very unique but I think as a whole he has a relatively unique kit. At the very least he's no less redundant than guys like Bucky or Rhodes.
Like, you and I were discussing "alternate hero skins" for the Avengers game over in the Games forum a few weeks back right? Well, you couldn't really make Falcon a skin for any of the game roster, his abilities don't overlap enough with anyone else.