One thing that I have noticed is that often in the PLC projects done by seasoned automation engineers the logic that would make sense to be represented as LD is

One thing that I have noticed is that often in the PLC projects done by seasoned automation engineers the logic that would make sense to be represented as LD is written directly as IL spaghetti code. I assume that this has to do with general unwieldiness of the LD editors in the vendors' IDEs. AFAIK the original idea behind LD is that you can do it on paper, and then hand-assemble the “bytecode” for the PLC and just manually key that into the PLC on some sort of octal/hexadecimal keypad without any kind of computer-like programming device. Obviously, this idea does not translate to present world with cheap and ubiquitous general purpose computers.