I dig the missions. As a struggling nub, a nice pile of credits is always welcome to help equip that next slot. When I end up low tier and have to spam APCR to pen, a fight can cost me 30k and I'm not exactly swimming in silver.
I think most of you here, however, are beyond that point where 60k credits or some crew boosters are of benefit. So yeah, I can see where missions might feel useless to you considering how many of you have said you have tens of millions of credits.
My missions always seem to fit what I'm doing though, while grinding the German mediums my missions have always been centered around V - X German tank things. Completing them just kind of always happened, there was never any pressure and it just felt like a little bonus.
It's a game, not a d!ck. Don't take it so hard.