You call Spring an outdated behemoth yet you have never worked with it. I've worked with EJB, Spring, Play, Dropwizard and a bunch of other stuff an I can tell that the current version of Spring is cutting edge and since they introduced java-based configuration you can really do stuff with it without the hassle which comes with other frameworks. Make yourself a favour and don't make a fool of yourself by bashing something you haven't even tried.
I can't agree enough. I can't find anything else with support that the Spring ecosystem has built for many cloud stacks (my experience is with AWS). Being able to choose from a whole host have identity providers, social, and other things for login and user data that generally just fits in to the normal auth and security mechanisms solves a problem we had for years with new applications.
It's certainly daunting if you're green to it and there isn't a grizzled vet around, but if you're trying to build for more than contrived simple solutions that you need to monitor, scale, and secure I don't know anything else out there that gets you so far down the road almost at the beginning.
I work with Spring everyday and really appreciate how it simplifies many things with enterprise Java development. However that appreciation has come with a cost.
In the original "Java Development with the Spring Framework" in 2005, it was argued that J2EE was far too complex in order to be effective. Spring was going to provide a simplifying framework to make development easier.
To me it's ironic how Spring has evolved in complexity over the years, but it's the first framework any of us turn to.