As the reason for using Docker, the author writes "The benefits of matching your development environment to your production one cannot be overstated". Again in my personal experience, this simply isn't an issue. Just use the same Python version and a roughly similar PostgreSQL version in development and production, and you're good to go.
In short, I feel OP would be better off without Docker. Once you know the rest of the stack well enough, you can set it up in dev and prod in such a way that you can trust that what works in dev will also work on prod. I've been doing this without problems for years.