Grinding credits and medals specifically really changed how it works for me. If you need medals, complete the harder missions fast and ignore the chaff, get the 10/15 medals per level.

I just ran trivial difficulty, flat bug maps looking for credits and medal drops, because you don't even have to extract to get them. Get the 30-40 creds, then exit to ship. Skips all the cinematics, and you can jump right back in to looting in a minute.