But parallel to that (and unfortunately-but-most-likely in lieu of): we simply shouldn't be losing large aircraft and having no idea what happened.
This results in a “don’t ask don’t tell” situation which can be even worse.
Maybe it doesn't nearly happen often enough to make this any kind of a priority?
Sub-total loss is presumably much more common and it’s useful there, but the adjustments to prevent it being disabled/make it more durable would be helpful there, too.
That seems to me like they might be at a sufficient level of durability already.
The recorders already to work really well for the purpose they're designed for.
The "bad actor in cockpit" plus "unexplained disappearance" scenario, for which they're not designed, simply doesn't happen often enough to be worthwhile worrying about.
Short version: flight recorders aren't broken, they don't need "fixing"
Long version: imagine you were to propose a major redesign to your employer's systems to attempt to diagnose unaccountable failures which based on historical data happen 0.00000018% of the time[0], what would be the response?
[0] back of napkin maths based on https://news.ycombinator.com/item?id=36284912
What’s the ratio like, 1:10000?