Gosh. So much this! The difference between the "average" PhD graduate in data science and the "average" software engineer with genuine experience delivering production software that people use at scale is quite something. I have nothing against data scientists, but in the same way that I wouldn't get a software engineer to build a complex model (above a certain level of complexity), neither would I get a data scientist to build a production app (above a certain level of scale). Both of these things are specialist activities that require a lot of experience, wisdom, and nuance to get right. Being good at one does not (necessarily) mean you will be good at the other.