Dependency injection is a fantastic pattern. It often allows you to easily unit test components that would otherwise require complicated mocking or stubbing.
It's worth stating that it's possible to use dependency injection without handing the object lifecycle and "wiring" over to a container. I always use dependency injection. However I would only consider using a dependency injection framework for a large project. For instance, last year I wrote a ~2k line webserver in Java and chose not to use "managed" dependency injection. My team agreed that this arrangement provided all the architectural benefits of dependency injection without the drawbacks of a DI framework (bloat, boilerplate, reflection, etc). However if it was 200k lines I may have made a different choice.
Since you're asking about the benefits of Spring and not DI/IoC in general, I have to say that I think Spring is poorly designed. The history of Spring goes hand in hand with the history of antipatterns and bad abstractions that have plagued the Enterprise Java community. To be fair, engineers that I respect have told me that Spring Boot is better. Certainly try it out, you will gain perspective on what does or doesn't work. But maybe also consider other options that adhere to the UNIX philosophy by focusing just on dependency injection.
