I'm super curious about what special features / extensions you're using. The only painful upgrade for me from PostgreSQL 7 to 9 (2010 IIRC, building from scratch with SSL library issues). My next upgrade (exact same database, evolved a lot in complexity with stored queries, views, ~500x size) was from 9 to 11 (2022), and it was totally painless. A few weeks ago I migrated it from 11 to 17, zero issues.

Edit: Oh, for reference, I'm not using docker, just an AWS EC2 Amazon Linux instance, with a mirror on an Alpine Linux server. PostgreSQL installed via package repo, very little custom configuration.