atceng;
As a proffessional control engineer (industrial) I have no hesitation in saying that the automation concept was prima facie to blame, and I am ashamed that such a tragic system was designed.
The automation FAILED, the pilots were RELYING on it and you must always be able to rely on it,until it detects a problem,announces it and relinquishes control. Any system which does not do this shoud never be installed in anything serious.
Well, you need to do just that: hesitate and think. Before launching, you need to understand the nature of the failure here. Radio Altimeter "failures", while not a regular occurence, are, and should be, a complete non-issue to a professional airline crew. It is, please understand, simply a non-event.
What is serious and has not been addressed by engineers but has been addressed by airlines, (in terms of emergency SOPs), is blocked pitot tubes and/or static ports. That issue will cause and has caused accidents; this very issue wrote off a perfectly serviceable $2b B2 bomber if you'll recall. That is an issue worth discussing; this one is most certainly not except for why this crew didn't fly their aircraft.
The plain fact is, this crew did not do their job; they abdicated their professional responsibilities and killed some of their passengers, because they stalled their aircraft, because, for whatever reason, they did nothing about a degrading airspeed. As someone else said, the CVR will tell the story but most bet we'll never read a transcript.
This crews' failure is in the same categorical nature and quality of professional failure that an engineer would be if s/he were to ignore/forget/mistake material strengths or span fracture mechanics. It is truly no more complex than that.