Which Warhammer 40,000 faction has the best infrastructure?

Which Warhammer 40,000 faction has the best infrastructure, and which has the worst?

There is no simple ranking: usable infrastructure depends on maintenance, upgrades, understanding and what each faction actually needs.

A clear ranking remains uncertain because the factions have different requirements. Necron infrastructure is theoretically excellent but decaying without adequate maintenance, while the Imperium possesses vast systems that often receive no upgrades. Ordinary improvements to tanks, equipment and armour should have continued regardless of the gene-seed changes associated with the Primaris project. The Tau are difficult to judge without knowing more about those who run their society. Orks need little conventional infrastructure. The Tyranids appear to be an entirely fleet-based organism, but too little is understood about them to assess their infrastructure or the full threat they pose. In this fictional comparison, inherited equipment, maintenance and continuing development need separate consideration. Uncertainty about an opponent's requirements also limits the usefulness of comparisons.