I’d argue if it was to be redone from scratch, we’d settle for hierarchical codes with country namespaces.

Probably something like us.lax, fr.cdg, ko.inc, or a combination of country + number HK02, GB231 etc.

Simple system get approved when there’s low friction in the ruling comitee, as it was the case when few countries were involved in the first place. Once more that 50 members need to agree on something restricting to 3 letters doesn’t work anymore and it becomes compromised after compromises until there is a hack to let each country deal with its own mess.