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Living on a coast has meant success to multiple human cultures over all of time. 
The ability to trade over water via building ports, have access to fish and salt and other resources has been essential for human development. 
IF we didn't live near water we wouldn't have advanced as far as we did.
Living on coasts or close to bodies of water is what allowed people to do international trade. Coastal cities, especially the big port cities which supported expeditions, are the reason we have modern science, medicine, food, trade, cultural exchange, etc. >

I think if your thesis was “it is a mistake to continue to settle and build on the coast” I would agree with you, but since your argument is “it was a mistake for human beings to live on the coast in the first place” I’m going to disagree. I the world was settled by seafaring people as well as land walking people. How many island nations would be completely empty if we just decided to stick to the mainland and away from the coast? How much trade, both of material, goods and ideas, wouldn’t have happened if we haven’t settled on the coast. 
Not all things have to happen for all time. Sometimes things come to an end, that were very good for a time. I think it’s perfectly OK to acknowledge that you need to change something moving forward, while also enjoying the benefits that something brought you in the past. >

This argument speaks to the need to carry forth historical progress via recogniztion of how obsolete systems no longer benefit us, which is important. My thesis was so extreme because I was thinking of events like the 1700 Cascadia quake. >

Even today a massive amount of trade happens at seaports. By value, 53% of US international imports come through seaports. That's hardly obsolete. And of course having seaports that handle hundreds of billions of dollars in international trade in turn requires labor for the ports, intermodal stations, etc. And that labor in turn has other needs like food, housing, entertainment, etc. which lead to other industries being present in port cities, at the very least to support labor related to seaport trade.
Maybe there's an argument that we should try to minimize how much industry develops around seaports and try to keep it to industries that directly rely on the ports, but that requires some pretty serious central planning, which generally doesn't end well. >

Tsunamis and hurricanes do not frequently happen on every single coast in the world. They are, in fact, relatively rare, especially before global warning. >

You ever notice how despite getting hit with hurricanes every year most of the coastal cities in the US don't need to be completely rebuilt? According to this article on Statista, about 300 people in the US died from hurricanes between 2016 and 2020 and that's on the high side for a 5 year span. Definitely tragic either way, but definitely a price worth paying for all of the benefits coastal living generates for a society. >

What I’m gathering is that from a rational perspective, which I don’t claim to have had while writing the post, hurricanes aren’t equivalent to something like gun violence. Gun violence can and should be reduced through policies, whereas hurricane deaths don’t prompt some mass movement to migrate inland. >

Well, it will always be a situation that has both benefits and risks. You have named some solid risks, now here are some benefits.
Science backed research  - (if you want some sources, just let me know but a quick google search pulls up many) shows there are many benefits to sleep, health, and mental states.
Location - Ports. Ports used to be the only way to get places across the sea, which was vital in human civilization expanding and becoming what it is today. 
Food - There's bountiful food in the ocean that allows people who live nearby to eat at better prices with good nutrients.
It is simply pretty - This one stands by itself and is completely dependent on the person who thinks it is desirable enough for this to be a benefit.
In response to these crisis, hopefully technology will help us improve on these points and allow them to subside to less than they currently are, and some technology already helps us see when a catastrophe will happen.
In the end however, it all depends on your personal cost/risk assessment of the above points (I'm sure there are more reasons than these, just a few off the top of my head). >

A fairly small amount of coast across the world is occasionally affected by natural disasters.
A fairly large amount of coast around the world allowed past civilizations to sail and trade and grow.
Fishing was a great resource for food when compared with the slow growth of plants and the need for land for animal husbandry.
Without coastal settling in history, humanity would not be as advanced and wide spread as it is now. >

Tsunamis and hurricanes are geographically very rare. Your entire argument is predicated on a narrow sliver of the world's coastline. You've created a cost benefit analysis and a prior decided the cost is infinite. It isn't. >


Sure, living on the coasts has benefits, but those benefits are outweighed by when tsunamis or hurricanes happen.

Let's use Scarborough, UK as an example. I'm not sure there's ever been a tsunami or hurricane there. Living on that coast has lots of benefits historically - including access for fishing, and sight of invaders. 
Whether continuing to live on that coast is a good thing is a different argument. Your argument is that settling there was a mistake and over a thousand years of history would suggest that is not the case. >

It happened thousands of years ago. Humanity is still here.
Even with a black swan event if all people living on the coast die somehow, theres still people elsewhere to repopulate. >

Something being fine for hundreds of years shows that it wasn't a mistake. >

Historically, cities had negative natural population increase. It's my understanding that this applies to most cities in most periods before modern times with sanitary and medical breakthroughs and food security. And it probably wasn't something that escaped notice in all this time.
So people just didn't care.