With Spring-Boot you can even start treating Spring and friends like a "Black Box", and stop caring about how it does what it does.
Springboot takes an opinionated approach to a lot of things, but always lets you override it and do whatever you want wherever you want.
I suppose that's more of a greybox...
You end up making your own framework that has all that in it, so that you just change a few things here and there and can start getting to the business logic that much quicker.
Then you realize you're maintaining all of that code... when you'd much rather maintain the business logic bits...
Which leads to using Spring Boot and letting them maintain everything else.