PG 11 is end-of-life, right? So you won't be getting new security updates.
What's worse, libraries will stop supporting it over time, so you'll find it difficult to stay up to date in other places in your stack.
If I was running PG 11 in production, I'd be looking to upgrade sooner rather than later. Being on older-but-stable versions is good risk management, being on end-of-life version is not.