It is up to date. Things haven't changed substantially, and they probably won't change soon either. There's nothing in the book that you'll have to unlearn or avoid applying.

Its an interesting book in that 2015 was in the middle of the noSQL hype. Since then, people have started looking for results and being more critical.

There's a gazillion technologies that we could list that are newer, and claims that any of them are the next big thing and will fundamentally change everything are, obviously, exaggerated.

You might look at the concept-oriented model [1] which is a major alternative to set-oriented approaches (including RM and MapReduce). Shortly, instead of viewing data processing as a graph of set operations, this approach treats it as a graph of operations on functions which make many data modeling/processing tasks simpler and more natural in comparision to the conventional purely set-oriented approach.

[1] Concept-oriented model: Modeling and processing data using functions: https://www.researchgate.net/publication/337336089_Concept-o...

(Disclaimer: I am the author)