According to this Stack Exchange post from last year a full IPv4 routing table requires on the order of a few hundred MBs of RAM. This is indeed a tiny fraction of the cost of maintaining the global internet infrastructure.

https://networkengineering.stackexchange.com/questions/76562...

The problem is that the routers that have to hold the routing table can only handle a limited number of routes. There is a good article from APNIC about the topic.

https://blog.apnic.net/2021/03/03/what-will-happen-when-the-...

Said routers could be redesigned...

And besides, there is no need to keep the whole routing table in RAM. Instead all that's necessary is a single integer per route representing which port packets to each route needs to be sent down. So even for a large router with 64 ports, the whole routing table fits inside 1 megabyte.

Sure they can create routers with more space for the routing table but you still have to replace all the old ones which isn't cheap.

A single port of a router at an internet exchange can reach more than 1000 different routers. A router has to decide to which IP it should forward a packet not just the port.

It's not "twisted into uselessness"... the reduction in routing table size comes from the large address space. No twisting was needed.

Also, the routing tables we're talking about here need to be stored in TCAM. Content-addressed memory is a lot more expensive than regular DRAM.