Too many people confuse the concept of DI with a DI framework.
You don't even need a DI framework to write straightforward programs in Java. After all, Java also has interfaces!
One of the reason people needed a DI framework in Java is crazy "enterprise" configurability requirements and Java EE-based standards that required you to implement a class with a default no-argument constructor. If you're using a web framework like Jooby, Http4k, Ktor or Vert.x, you do not need a DI framework (source: we've written many modern Kotlin applications without a DI framework and we've had zero issues with that).
Of course, all of our non-toy Go applications are using dependency injection as well. Unless the code reviewer messes up, we won't let anyone configure behavior through globals and singletons.
> One of the reason people needed a DI framework in Java is crazy "enterprise" configurability requirements a
No, it's so that you can have something else manage the lifetime and disposal of your services instead of doing this yourself. You don't have to be writing crazy enterprisey code to have the need for this.
I agree DI is simple, but 100% disagree that you can achieve this through a hand-rolled library without sinking a ton of wasted time.
DI is necessary in every language that doesn't rely solely on global singletons. Passing dependencies as arguments to a function is DI.
What may not be necessary, are IOC containers automatically create objects and satisfy their dependencies.