My impression is that the field is more disciplined in terms of knowledge now than it was ~8 years ago - the fundamentals are better understood and more clearly expressed in literature.
Also there are still plenty of topics on which the new techniques can probably be fruitfully applied, especially if you have some domain knowledge that the math/CS PhDs don’t have.
For OP - I’m in a similar situation and have been going through Kevin Murphy’s “Probabilistic Machine Learning”, which is pretty massive and dense but also very lucid.