Earlier quoted context omitted.
I think the feedback was, this looks like a very simple (but possibly useful) app, it should not have such heavy dependencies.
What's heavy about any of that? I don't know what Tomcat is, but Docker is just a means of installing and running software in a VM(if host isn't Linux), Java is a perfectly fine language and runtime, and Postgres is a powerful and widely-used database. Any other self-hosted web app would require at least a language runtime and a database.
To me, size of the image is more important than the number of servers in it.