More conext please, just naming an armor doesn’t tell me anything.
It’s not that you can’t walk, it’s that your agility is impaired. Desire for mobility doesn’t stop modern armies from saddling infantry with in excess of 100lbs of gear, see https://mwi.usma.edu/the-overweight-infantryman/
This is the reason for power armor more than anything, the desire for more armor is just one aspect of it. Your assertion that agility is a top priority is simply not supported anywhere in modern military doctorine, which is what the source of power armor in DDA is based on.
You’re conflating tactical mobility (taking cover, obstacle avoidance, access to difficult areas) with agility (manuvering while fighting, close quarters combat, dodging). High encumbrance might hinder the first, but it pretty much entirely cancels out the second, and that’s fine, modern armed forces don’t expect you to try and dodge things because that doesn’t matter on the modern battlefield.
That’s fallout, and dda simply doesn’t handle fallout.