You seem to have be missing a fundamental thing about tech but I can’t pin down what it is. So I will respond to your edits.

but I can’t buy a static address that will persist across networks endpoint changes

You can. It’s called Provider Independent Space and it a pain to go with as an individual.

Yes, it would be a privacy nightmare, I want to know why it didnt turn out that way

Because people smarter than you, I, and everyone else in this post said 'Yes EUI-64 is a good idea in principe but the problems on a privacy perspective outweigh the advantages. So let’s build a system called MAC randomisation so people can get multiple address to access the internet with. ’
The good news is you can turn off MAC randomisation.

AFAIK IP addresses (even static public ones) are not equivlent to phone numbers. I don’t get a new phone number every time I connect to a new cell tower

In some parts of the world or before 2000 if you changed mobile providers, say from Vodafone to Telstra you had to get a new number. Since that change number routing has become a nightmare and it makes the BGPv4 table look sane in comparison.

Even if a static IP is assigned to a device, my understanding is that connecting the device to a new uncontrolled WiFi, especially a router with a NAT, will make it so that people who try to connect to the static IP will simply fail.

This is a complex one due to NAT in the ipv4 space. NAT exists purely to allow devices to have the same private IPv4 address and hide behind a public v4 address.

No, MAC addresses are not equivalent phone numbers. 1. Phone numbers have one unique owner, MAC addresses can have many owners because they can be changed at any time to any thing on most laptops. 2. A message can’t be sent directly to a MAC address in the same way as a phone number

1. MAC do have unique owner blocks. Cisco somewhat owned the 0000.0C block.
2. Yes you can. That is literally how it works down the TCP/IP stack.

Yes, IMEI is unique, but my laptop doesn’t have one and even if it did its not the same as an eSim or sim card. We can send a message to an activated Sim, we can’t send a message to an IMEI or serial number

If your laptop has a regular Sim slot it will have an IMEI. True we can’t send messages via IMEI or serial because those systems were never designed for message routing.