I think this is one of those situations where you may not be able to assign fault to any one set of people. Remember that everyone here has the clear advantage of knowing what went wrong and how, the people who designed this may not have forseen any such situation. Also one of these systems, even something as "simple" as MCAS would have involved dozens if not hundreds of engineers in all the design decisions that lead to this issue, including many people who have already retired or done so long ago (remember, the 737 was originally designed in the 60's).
The desire to assign fault to one individual and punish them is a very emotional response to this situation, it means people will not accept that it was an unforseen or systemic issue (people familiar with air crashes have seen in the past some systemic issues, where everyone did everything how they were supposed to but things still went south) without some individuals to blame. Typically crash investigations try to ferret out all points of failure, you might read "pilot error" in the news, but rarely is that the only cause in the crash report.
For example, this crash:
https://en.wikipedia.org/wiki/American_Airlines_Flight_965
It identifies some training issues (automation dependence, speedbrakes still being applied while executing terrain avoidance maneuver) but also identifies issues with the FMS in how it manages waypoints and how they are named.
So, for the current situation there are obviously many aspects to be addressed:
1. MCAS software appears to do more than specified, this is apparently what the software update (delayed by the government shutdown apparently) is to fix.
2. Pilots need to be trained or retained on stabilizer trim runaway.
3. The 3 AoA sensor option might need to be mandatory on the 737 MAX.
4. The FAA may need to review their effective supervision of both Boeing and the air carriers.