They’ll have to adapt like every other generation has had to
My grandmother was born in 1924 and died in 2019 please appreciate how much change she had to adapt to over that period
Your grandma had plenty of opportunities in the post war eras. During her time there was always a need for human workers. While I dont think AI can actually replace anyone reliably, I still can see how executives buy into this promise and try it. This is a unique situation humanity never was confronted with. Even the industrialization required a lot of human work. If all white collar jobs went away there is a huge imbalance in available workers vs available work. Simply adapting to this isn't a thing given that monopolies killed competition and its not feasible for your everyday Joe to break into markets anymore. Kudos to your grandma for making it this long, simply not a comparable situation however.
And when did work done by humans stop existing between 1924 and 1990? Because that's the type of change we are talking about.