John Morehouse keeps one eye on things:
Contained availability groups solve some real operational problems, especially around logins, jobs, permissions, and supporting metadata. They can reduce drift between replicas and make failover cleaner.
That does not mean they are magic.
Like most SQL Server features, contained availability groups come with details that matter. The feature can absolutely help, but it needs to be designed, tested, and operated with the right expectations.
Click through for several things you should consider before jumping into deploying contained AGs.