A big part of why people keep using spring is simply put: the amount of code that exists, along with SO Q&A. That alone is a big pro that very few frameworks/libraries can boast of.
In no way am I endorsing spring. I haven’t used it in any form over the years, and honestly don’t see the need for it. But that is in the bubble of having developers that are very experienced and existing code that does things without lots of frameworks.
Just remember that frameworks are tools, not a cult. If spring solves your problem, then that’s the answer. If http4k does, then that’s the answer.