replacing manual laborers with more thinkers/designers. The work will be easier, but there will likely be a lot more of it.
I will not even go into detail of you argument because the situation is much more complicated and reasoning is flawed.
But imagine world with 6 bllions of thinkers/designers ?
How do you see everyone will have an opportunity for job to survive ? Useful jobs i might not not useless like marketers bankers or lawyers.