My point is that this general sketch of a layout with arrays of offset pointers roughly generalizes to something like a B or B+-tree fairly well, and that's a fairly simple data structure. You can absolutely implement a file system with passable performance with either of those tree structures.

( Here's an enjoyably lucid explanation on how to draw such an owl: https://www.youtube.com/watch?v=aZjYr87r1b8 )