I agree. It would have been better to bind a key to each scorestreak slot rather than one to choose and another to activate. It's a bit frustrating when to want to use the sentry gun, for example, when enemies are rushing at you but you pull out a care package marker.
I think this was an EXTREMELY silly mistake to make, after all it requires 3 buttons to scroll through and activate one (1 = prev, 2 = next, 3 = activate), but there are only 3 scorestreaks, so why force us to look at the corner of the screen, watch it while we take half a second to change the selection, then activate it (up to 3 keypresses) when we could just press a single button to use the exact one we want?
Sure, occasionally you might get one extra scorestreak from a care package or something, in that case I'd be happy to just have one extra keybind for it.
It would be great if we could get it changed, and even better if they give us the option to go with either method (keep the current method, but add 4 new binds for the people that choose to use them).
Other than that, I really like what they've done. Keep up the good work, Treyarch!