This is analogous to bitching that a sturmpio will win against riflemen up close.
Sturmpioneers are not OKW's main line infantry. Attempting to treat them as such will not get you far.
That is by design, and moving/positioning your units based on the situation is more or less the entire concept of the game/genre.
So basically Ostheer should only ever have units in green cover, even though they cannot make green cover?
Or maybe they're supposed to build bunkers to house Grenadiers, which are totally free and not vulnerable to Grenades.