Even then, your own definition of shit jobs, " low pay, but high effort, manual, dangerous, etc." doesn't really correspond that well.
High effort and dangerous jobs usually pay well... low paying jobs are inherently manual, and/or likely to be automated away. In the end, some things don't automate well. There's a human aspect to a lot of things, and many of those won't be displaced soon. Of course, I do understand that many other jobs cannot fill the void that will be lost, especially with an ever expanding population.
It all depends on the ratio "Ease-of-implementation" / "Cost of existing manpower" for each sector of job.