They do lack a theory of program. But also, if there's one consistent theme that you can trace through my 25 of studying and working in ML/AI/whateveryouwanttocallit, it's that symbolic reasoning isn't nearly as critical to building useful tools as we like to think it is.

In other words, I would be wrong of me to assume that the only way I can think of to go about solving a problem is the only way to do it.