I think the improvement new stacks are bringing are getting more and more marginal, compared to the effort required to learn them, and instead of learning those

I think the improvement new stacks are bringing are getting more and more marginal, compared to the effort required to learn them, and instead of learning those new framework, I would rather spend time learning about new fields in programming; for example the things I am interested are, in no particular order: neural networks, compilers, 3D graphics, high performance computing, and maybe crypto and OS development.