I'm not an expert, but I think this is fairly typical. Unless any of that wood is actively rotting (which would indicate a larger moisture issue that needs to be addressed), using old ugly boards to stabilize and level cabinets and countertops would seem to me like the appropriate approach during installation.
It looks like this was a remodel? If so, they definitely wouldn't have bothered to make anything look pretty if it's going to be hidden behind cabinets.
In other words - it's probably not as bad as it looks. If it ain't broke, don't fix it.