Some cultists making a body with sacrifices or stuff every time is exactly what it means, I think.
Angels are said to be big undertakings involving a lot of investment and interlocking Infrastructure on the GMs part, which is probably why they're usually saved for the important jobs rather than just thrown at everything.
Infrastructure can be really weird and varied though. Some might look like an esoteric Christian mystic movement doing rituals to 'summon' an angel, some might resemble a top-secret weapons research and development site staffed by scientists who think they're working for a government conspiracy into researching new alloys, some might piggy-back off a regular construction firm or local council, getting them to design buildings and roads just so and they then channel weird occult energies into the process.
One Angel might require all of these and more at the same time to be built, maybe even in locations spread through the country or world and another project being needed to bring the elements together. The GM is big and weird like that.