For the longest time, I was primarily focused on the Spring ecosystem only; that's why the Spring course material is so extensive. 
And, yes, that made Baeldung one of the best ways to both get into Spring Boot and explore the advanced aspects of the framework. 
So, overall, I think it was the right decision, but… it definitely wasn't enough. 

Spring is a core part of the Java ecosystem, yes. But, there's so much more to working professionally within the Java ecosystem than just Spring. 
A strong understanding of testing, with JUnit and Mockito. 
A practical use of Maven to build the project. 
Shaping JSON well with Jackson. 
Deeply understanding collections and streams in Java. IO. Concurrency. 
SOLID principles. Architecture. Good logging practices - one of the most underrated skills a developer can learn. 
And a lot more. 

Baeldung is quickly becoming the de-facto course platform to learn and grow as a Java developer, through: 
>> Baeldung All Access (during Black Friday)


Also have a look at the upcoming courses on the roadmap: The Course Roadmap. That's evolving fast. 

Enjoy, 
Eugen.