And, how many maps actually allow you to build it in key positions that actually have enough open room? Not so many... with 20 pop and no shooting through everything. I'd rather have a pak43 replica that costs 0 fuel (down from 75) that can shoot through everything.
And it's not strong in the open because it becomes an easy target for mortars, arty, AT, JT outranges it?...
Takes a simple barrage to decrew a pak 43 (Assuming there aren't infantry near it, so it's pretty much lost.) Takes lots of barrages to destroy 17 pounder. It shouldn't be a problem considering you'd get anvil engineers to repair it once the barrages stop. And if you're still having problems with artillery, try placing it further back, and (or) pushing to destroy the Artillery instead of turtling.