The Derelict, both in Isolation and Alien 1979 is moist, battered and overall seems... Derelict.
Like a scratched up vehicle, there's no way to know if the damage is functional or just weathering
but it gives the impression of an old abandoned haunted house that logically should crumble but... yet, doesn't.
You're probably right in that Prometheus' Juggernaut's interior is likely inoperable even if the exterior is seamless.
And I believe to a degree, the Covenant Juggernaut is part theatre on David's part - luring the Covenant certainly is.
Which makes me wonder if somehow David engineered events to attract a ship.