The fact is that already in 1993 routing tables were just too big, and the fact is that having a "flat" address space was always going to mean huge routing tables, and the fact is that because IPv6 is still "flat" routing tables only got larger.
The fix would have been to have a subset of the address space that is routed as usual for bootstrapping ex-router address->AS number mapping, and then do all other routing on the basis of AS numbers _only_. This would have allowed us to move prefix->AS number mappings into.. well, DNS or something like it (DNS sucks for prefix mapping, but it could have been extended to not suck for prefix mapping), and all routing would be done based on AS numbers, making routing tables in routers _very small_ by comparison to now. Border routers could then have had tiny amounts of RAM and worked just fine. The IP packets could have borne AS numbers in addition to IP addresses, and all the routers in the middle would use only the AS numbers, and all the routers at the destination AS would know the routes to the destination IPs.
But, no. Great missed chance.
Well, we still could do this with IPv6, but it would be a lot of heavy lifting now.
EDIT: Ah, I see draft-savola-multi6-asn-pi existed.
EDIT: Ah, see also LISP [https://www.rfc-editor.org/rfc/rfc6830]. But LISP is essentially dead.