Writing, supervising and training LLMs are now the purview of... even larger LLMs. Optimising CUDA kernels; hand-writing SIMD assembly to speed up data loading; tinkering with your particular brand of DRAM to see if there's anything to gain from optimising for its memory topology and NUMA --- these are now the job of AI.

There is very little reason for humans to get all too engrossed in this type of work now, today, with the hope of being good enough at it to command a high salary in 3-5 years. AI can already do it incredibly well, and they can do it persistently and doggedly 24 hours a day.