Some people who don't use AI will be left behind - those who work on things where LLM's are capable of a substantial amount of the tasks will be left behind if they just refuse to leverage the superhuman properties that LLMs have.

I don't think it's hard to catch up if such a person changes their mind, though.

Some people who do use AI will be also left behind - those who use it to replace their skills without developing new ones themselves, and those who use it to do the same or worse work more cheaply. They will be left behind in a competitive world where others will work out how use it to do more or better work with no reduction in effort.