Comment by JustExAWS
They can choose jobs. Starting with my 3rd job in 2008, I always chose my employer based on how it would help me get my n+1 job and that was based on tech stack I would be using.
Once a saw a misalignment between market demands and current tech stack my employer was using, I changed jobs. I’m on job #10 now.
If one wants to optimise career, isn't it better to become an expert in the _less_ mainstream technologies that not-everyone can use?