I don't see why you would need a graduate degree to create a new PL that compiles to machine code. In fact, many successful PL designers lack PhDs.

Most work in CS feeds more on experience than education. A PhD is simply a way of getting deep experience (and advice) in areas that a job probably wouldn't allow for. Since ML is hot, you can get hands on experience with it these days, its not like 10 years ago when the only people looking at deep learning were pretty much researchers, PhDs, and PhD students.

That is also taught to a useful level in undergraduate coursework. You can do useful ML using only first year undergraduate statistics, linear algebra, and multivariate calculus.