As automation via AI and the autonomous robot workforce slowly comes online, both of which are happening, these "basic jobs" will also become obsolete or automated. Jobs will increasingly shift to the STEM and away from workers on industrial lines or there will be extremely limited numbers of workers basically acting as overwatch; this can already be seen in a number of places where large factories are basically managed by 10-20 people unless theres large construction/expansion. This will become more prominent, as can be seen by the dark factories already in the works or partially operational. Many industrial jobs are going away, and people who have been in those industries their whole lives will not easily find other careers. UBI guarantees you can at least minimally survive without work, which is important during those periods where people are having to learn new industries to survive as their jobs are removed by automations.

Manufacturing isnt going anywhere, but it will increasingly take fewer and fewer people to operate and build many things.

UBJ would work in some cases where your knowledge could be (relatively) easily applied in other places, but we basically already have a partial implementation of UBJ, you can easily get employment assistance from almost any state in the US, but its also trying to do the same for 5+% of the human workforce at the same time. Sometimes it can be many weeks or even a few months to get something; what can a person already not making a lot do in that case? With UBI the stress is alleviated, and can help bolster the persons living situation when out of work.