You have been writing web automated tests for a while.
You are using
Java as a programming language
TestNG as a unit testing library
Selenium WebDriver as the browser automation library
Since you are getting good at this, you may be wondering what else should you learn.
What is the next big thing for you?
To answer that, let's see what your current situation is.
1. Project dependencies
Your project uses 3 dependencies for now, Selenium WebDriver, TestNG and the Java libraries.
These libraries are usually attached as jar files to the project.
They also change in time.
Every time a library changes, its version is increased so you need to download the new library jar file, remove the old one from the project and import the new.
This is not so bad if you have only 3 dependencies.
But in a real automation project, you may have 100 dependencies that change all the time.
Imagine replacing all of them once per month.
What a tedious task!
It would be nice if there would be an easier and fast way of keeping the dependencies up to date for your project.
2. Execution of tests
You have a suite of tests and you execute it frequently in Eclipse.
This is good for now.
But in the future, you will want to run the same tests in a CI/CD environment which typically does not have Eclipse installed.
How will you do that?
3. Project structure
Your project has test classes and page classes.
Probably not too many at this point.
The more work you do, the more test classes and page classes you will create.
And to reduce code duplication in page classes mostly, you will start creating common purpose classes and group them in a framework.
How should you organize all these classes?
How should you design your project?
4. Share your framework across multiple projects
The company you work for may have multiple web sites that need test automation.
You will have an automation project for each site.
However, you would like to share your automation framework across projects so you do not duplicate the framework code.
How can you do this?
5. Project artifacts clean up
While running your automated tests, artifacts like screenshots, logs, json files, html files are being collected.
You will need a way of dealing with these artifacts which in most cases are not useful.
You should clean them up after each build.
How do you do this?
Coming back to the question on what should be next for you.
You should learn the tool that provides an easy and elegant solution to all these problems.