Re: Starfleet Marine Corps
Why you keep saying this? Why is this the only thing they can do? If a Starfleet pilot can fly anything from a huge starship to a shuttle and even to a 20th century helicopter, I'd assume the security personnel to be pretty diversely trained too.
Not everyone is like Sulu.
As for the redshirts: They were incompetent because they always went off wandering on their own and were thus the first people to get killed by the alien rock monster thingy or whatever. Real soldiers wouldn't die that easily.
"If the world was perfect, it wouldn't be." - Yogi Berra