I’m not sure you understand. A pilot can shut off any individual system they want if it has a problem. In this case the correct action IF something like this happens is to shut off the affected system; that is, the ADIRU. And yes, that would solve the problem. You can even turn off an entire main flight computer (the aircraft has 2) if it’s causing problems and switch to the other one. There are lots of other computers on a plane too (each of the three ADIRUs is effectively its own computer, for example), and they can all be shut off. So I’m not sure what your complaint is about being “unable to shut off the computer.” As for a bulletin, that’s literally just how manufacturers disseminate information to airlines and pilots. This is basic stuff, it’s not some kind of negligence.
I think you also don’t understand how hard it is to make a system that is absolutely fault-proof. Literally every electronic system ever built and designed is potentially vulnerable to random space particle impacts. You can TRY to design a system that’s resistant to them, but we only sort of even know how. You can then build a system with a hundred built in checks to filter out any bad data in the unlikely event that some is generated, but there can always be an edge case that even a seasoned team of engineers will not think of. If you think it’s a manufacturer’s responsibility to build a plane that can literally never fail, and that anything short of that is negligence, then frankly you don’t understand how the world works — because that is impossible. Nothing will ever have a failure rate of 0%. The best you can do is keep adding more and more layers of protection until the probability of a failure becomes so incredibly low that it’s not a concern. Statistics do mean something.
So this was a case of a completely unforeseen issue that was difficult to predict, killed no one, and now that it’s known, has a very simple and effective band-aid type fix while engineers work on more reliable systems. There is simply no reason for me to lob any serious criticism at the manufacturer here.