While I'm not old, I have been a professional developer for 17 years and feel that first downwards curve in the author's graph (and I get frustrated at the younger programmer's reinventing the wheel from time to time).
However, I never find myself confronted with things that are not genuinely new and interesting to learn and work on. A lot of these things are not new at all, but they are new to me: statistics, linear algebra, machine learning, compiler construction, PL research, model verification, graph algorithms, calculus, engineering modeling, vectorized programming, GPU programming, geometrical computation, and it just goes on and on. In each of those, you will have the fads of the day, the current hot framework, the second current hot framework, the old framework that works better. At the end of the day, I get the textbook, look up university courses on youtube, pick whatever framework shows up first in google, and spend time on the fundamentals. As a crude example, I may have to look up how to do a dot product in numpy / matlab / mathematica / c++ / R every second day, and when i learn something most of my programming is SO-driven, but I also can perfectly write a dot-product in clojure/factor/elixir/arm assembly if you asked me to, and then do a vectorized dot-product in CUDA/Neon SIMD/VHDL because I spent time on the fundamentals. The best thing that happens is when you start to see how one technique appears in so many different fields (for example SVD).
Nothing is new, but most of it is new to me.
After that I do spend a significant amount of time researching my tools (IDE, supporting apps, build systems, frameworks, compilers, programming languages), but that's the craftmanship part of it, and is kind of like doing the dishes and going to the farmer's market to have a nice kitchen to cook in and great ingredients to cook with.