They allow you to, but on every single flight I’ve been on in ages, the pilot makes a note that they recommend keeping your seatbelt fastened whenever you’re seated. People have been injured due to sudden and unforeseen turbulence, and it’s just a good idea in general.
That said this incident occurred during the initial climb-out where seat belt use is mandatory.
So yes, if a passenger was seated there and if their belt was unbuckled, I can see how somebody would have died. Nobody is saying that this isn’t a serious fuckup that doesn’t need to be investigated and remedied.
What I am saying is that major airlines in the U.S. have a more or less unblemished safety record for twenty two years, the likes of which has not only been unparalleled in aviation, but by any other form of transport. Literally walking is more dangerous than flying a major commercial airline in the U.S.
The MAX line of planes in particular has had their share of problems, but with the MCAS situation resolved there is no reason to believe that it in particular is any less safe than any other airframe operated by the majors. The issue with the door plug is unlikely to be related to the MAX (the same part and design have been in service without issue since well before the MAX). It will be investigated, fixed, and we will in all likelihood go back to flying gajillions of passenger miles without serious incident.
I’ll put this another way: if all of this gnashing of teeth and doom and gloom causes enough anxiety over flying that a few hundred people choose to drive instead, it will inevitably cause more injury and death than if every airline went all-in on a fleet of 737 MAXes.