I may be wrong, but it looks like laying eggs is just like pooping. The is gonna come out no matter if your nest is ready or not. Maybe this pigeon had its nest destroyed and did the best it could to build another one.
Pigeons are notoriously bad at building nests, because they don’t have to good like other birds.they are descendants of Rock Doves (kewl name for a band) and like their ancestors the just need a flat surface and are use to dealing with meager building materials. They use what they have for a “good enough for me” nest and pigeons being almost everywhere in the world means their nests do just fine.
It's unfair to call them shitty, rock pigeons make nests on flat, stable surfaces, and are tended to by both parents in shifts, so all the nest needs to do is prevent the egg from rolling away when they get up. The nests are perfectly suited to purpose, it's us humans who are imposing unfair beauty standards for what a nest "should" be.