I think job requirements evolve based on who is available in the market, and based on how quickly and how willing a typical hire is to move to your tech stack.

I think job requirements evolve based on who is available in the market, and based on how quickly and how willing a typical hire is to move to your tech stack. If people with specific experience are available, companies will tend to hire those first - lower risk from their viewpoint; otherwise training becomes a necessity. Expected tenure is also a big factor - if a company seeks to recruit long-term employees than the criteria will be very different: they will focus more on ability to learn and adapt, team work, communication skills and leadership ability than on short term tech stack.