I think optimizing layout or at least attempting to minimize the amount of crossed conveyors is most of the issue.
Yup that's exactly what I was thinking about. If you don't have to optimize, then you can mix and match heuristics to get the job done. If you have to optimize... now the search space gets real big real fast.
I work with a rather complex database in my day job and occasionally maintain a very human-oriented ERD for employee education - I've looked at various auto-ERDs in the past and failed to find one that can actually produce a decently pleasant visual diagram as output - most of them will just give up on the task and lay tables out in a roughly hierarchical display based on distance from a relatively core table and then let links between tables lie where they may.
Optimizing layout is a very interesting problem and one interest component in Factorio in particular is that you have some real values to measure as output like:
1. Total space used
2. Total energy required (more inserters means more power - more belts usually means more space)
3. Throughput
4. Pollution produced
5. Tile-ability of the design.
6. Proportion of unused space within a bounding box
Probably a few other fun ones - it actually sounds like a pretty approachable problem to get objectively good results out of.
Yup that's exactly what I was thinking about. If you don't have to optimize, then you can mix and match heuristics to get the job done. If you have to optimize... now the search space gets real big real fast.