The problems in the FAA start with the US Congress and end with the US Congress. They underfund the FAA and saddle them with responsibilities and then wash their own hands of responsibility and cave to lobbyists if the FAA isn't keeping up with corporate support**. Unfortunately the Pollyanna concept that voters have any influence over such operational details was swept completely away by Citizens United.
Airlines (most of them) and manufacturers have huge incentives to not cause a crash. In the design and operation there are literally on the order of a billion decisions. To review those requires a staff/skill level that is even larger. That oversight is expected to review to see if the decisions made are correct, but also to discover the decisions that weren't made at all.
If the decision tree for MCAS had added "Crew won't trim and won't reduce thrust," particularly after LNI610, then the workable solution wasn't to remind crews about how to manage trim runaway but to simply disable electric trim for all flights. However no one noticed that branch was missing, so no one made a decision based on it.
Missing decisions are the most difficult problems to find.
As to work-load. This could be reduced if the FAA required industry to include them on automated tools that track approval status. At the time MCAS was being prepared the software would have been in a software controlled vault that required multiple approvals to advance through the process. Such systems can send e-mails to a list of participants and can include the differences between versions to make understanding the changes simpler. None of the recommendations in Report AV2023025 suggest any such automated manner to ensure all parties get unfiltered information. This is an enhancement to lengthy status reports that might miss or minimize details.
I expect that with full disclosure the FAA would not have identified the potential interaction between a valid, but incorrect AoA sensor and MCAS. By avoiding a paper trail the FAA avoids responsibility.
**This is why the FAA has worked on eliminating R/C hobby fliers in the US and ignoring that as many people die in GA accidents in the USA each year as died on the two 737 MAX aircraft, including several avoidable mid-air collisions every year.