PCB layout is a weird problem. As the article says, you can get halfway through before realizing you need to re-do everything, and there's no way to predict that from the outset. It's an inherently self-bottlenecked process.
There is also a lot of judgement that goes into it, that I'm not sure could ever be fully covered with AI. You can never hit 100% perfection on every metric (crosstalk, parasitics, DFM, BOM optimization, trace length matching, etc.) so determining where and by how much these things can fall short of optimal is very much a part of the process, and seems like it would be an overfitting nightmare for an AI.
There are also simply decisions that have no empirical right or wrong answer, but are still critical to the system functioning. What frequency do you want to run your data busses at? How much power can it draw? How long does it need to last in standby? How hot can it get?