And yet your phone could compute the next 100 years of this ethereum GoL calculations in far less than a second!
Sure, it's a very different beast, but I still find it really _cool_.
That being said, The Paris Agreement and I hope you’re right.
Meanwhile, most of todays blockchains will be dead. No nodes left to sync with. Maybe the blockchain concept will live on in a new form, but even now, there seem to be dying blockchains that are very difficult to connect to and use (e.g. Dogecoin, at least before the recent price surge)
I guess a real threat to all historical code would be the end of open computing, and the requirement for any code run anywhere to be signed and censored by a megacorporation. Something we're getting worryingly close to. But in that world, most of today's blockchains will quickly die, too.