When the Occupational Upgrade preview went live it added two substantial changes to the way dupes worked and how they interacted with the world.
First was the introduction of jobs. Now jobs could be assigned to dupes and they would get bonus associated with that job, usually in the form of stat bonuses. The second was a revamped priority system. The priority range was changed from 1 through 9 to 1 through 5 but functioned on two levels. Dupes would now do tasks for their job from priority 5 down to 1 before doing any other tasks from priority 5 down to 1, a strict toggle for priorities was introduced to have tasks marked with it be treated as if it was part of every dupes job.
Now there were some problems with the jobs and new priority system. Stat growth for dupes that used to be there was removed, leaving dupes painfully slow. And dupes would not treat tasks that were required for their job's tasks as part of their job, like the delivery of materials to something that was part of their job. The priority problem was fixed relatively fast and Dupes would do tasks required for their job tasks (cannot find a source but I was told that that was the case).
But about halfway through the preview, they scraped the new priority system. They reverted to the 1-9 system with the slight tweak that dupes would prefer, at the same priority level, task related to their job over other tasks. Jobs were also tweaked. Stat growth was returned in a limited fashion (capped to 20) and dupes now retained the bonuses from any job they mastered.
Then in the In the final release, they reverted the priority system fully to what was before the preview.
The new job system puts restrictions in place that require a more flexible and nuanced priority system. We had that with the new system they introduced, but it got reverted and now we are left with half of a system good system. Klei has stated that "[the new priority system] was hard to understand, and now that we've added the ability to retain mastery it didn’t make much sense anymore, so we are going to backburner reviewing priorities for a later update." Therefore, let's see if we can help Klei out and come up with a better priority system.
Honestly, it is simple. Reinstate the new priority system. The problem was not the priority system, the problem was its explanation. The new priority system was not that hard to understand, I did not even play the preview and was able to piece it together from reading on these forums. So if it was hard for people to understand then it was the explanation of the system, not the system itself. On top of that, the skill curve in this game is understanding how the systems work and manipulating them to your advantage. As long as people understand the basics the more complex parts can be figured out by observation and experimentation.
It is probably not the case, but the speed of the reversion sure feels like Klei caved into a knee-jerk reaction...