neutral walls were really interesting of a strategic asset in supcom.
it allowed you to funnel units to where you wanted and slowed their progression (as they'd have to destroy them first) if they wanted to move through
they synergized strongly both with units and static defenses. they had tons of uses.
I get that the terrain is currently too cramped for there to be a need for much more blockage but that's a bad map design and scale problem not a gameplay one.