it should have been necessary
Mais avec qui il aurait fallu que je couche pour avoir une job comme ça ?
But who would I have had to sleep with to get a job like that?
— Les Invasions barbares (2003)
Il aurait fallu que je te remarque, mais oui.
I should have noticed you, but yes.
— Douleur et gloire (2019)
Il aurait fallu prévenir avant, pas après.
They should have warned us beforehand, not after.