Logical replication solves this. You roll the cluster, downtime is minimal. like 60s maybe.

Logical replication needs a special 'upgrade' use case that will automate most of its pain points away. I understand why DDL does not replicate, and that you may want to replicate to a data warehouse that only needs some columns, etc, but there should be a case just for upgrading that handles all DDL, sequences all existing everything, and just works...