I guess I just don't believe you, and it will take more than people complaining to convince me. In the situation described in this thread, I cannot imagine everyone in Central Park dismissing this notification without anyone saying "hang on everyone, it says missile instead of amber this time". I have lived in several big cities in the US and have gotten these alerts less than once a month, sometimes with years in between. It is not a scourge on society. I do think you should be able to disable them, but I think that even if explicitly given the option, most people would leave them on.

Fwiw, I stopped looking at them when I got the 4th or 5th one. I got good at sliding to unlock and silence the alert without even looking.

Once I found out that I could disable them, I turned them off entirely.

I'd be more okay with them if they didn't all use that horrible klaxon noise. That noise usually indicates an immediate threat to life, which doesn't feel appropriate for Amber or Silver (which indicate a potential threat to a particular person's life in a rather large area). Save the klaxon for "we're getting nuked" and tornadoes.

That might be a country or phone-specific thing, with various Android phones in the US I've never gotten any kind of sound, just persistent buzzing until you dismiss it.

If you knew the alert could be about something hundreds of km's away, and that it usually is, it's very likely people would instinctively turn off the very loud alert instinctively. There's a reason why "alert fatigue" exists. And it has been documented in tons of different settings. Too many alerts and warnings are worse than none. Is there any reason to believe the same phenomenon wouldn't happen in this case?

Yes, because they happen so infrequently and are widely known to only be used for alerts that most people think are actually important, even if they aren't always relevant to every recipient.