Really? I'm doing Java contract work for a living (thankfully not only Java) and, while it pays the bills, I'd use almost anything else (except .net which is just Java without the ecosystem). I think the whole Java stack, with its myriad of metaprogramming silos, overreaching build pipelines, outdated HTTP libs and paradigms, absurd class loader configs and layers of module systems, unsound abstractions, and third-party libs, many of which are starting to reach EOL, really stinks and sends you into a world of incidental complexity. It might not be so obvious if you're coding greenfield Spring "microservice" apps or, good forbid, Spring MVC apps in 2019, but believe me it'll hurt you down the road once you need to update your project to newer versions of third-party libs.
The problem with Spring isn't that it's badly developed (it isn't, and usually gives you good diagnostics, though your stack traces gets spoiled with Spring's ugly-as-sin reflection shite). The problem is that there are people who think Spring has a reason to exist in the first place. Spring Boot is a config framework on top of the Spring framework to make it bearable - that alone should tell you to stay away from it.
I know all too well ); Only three years ago I contracted for an insurance company for JSF, and worse, using portlets under Websfear. Well, it payed the bills.
The problem with Spring isn't that it's badly developed (it isn't, and usually gives you good diagnostics, though your stack traces gets spoiled with Spring's ugly-as-sin reflection shite). The problem is that there are people who think Spring has a reason to exist in the first place. Spring Boot is a config framework on top of the Spring framework to make it bearable - that alone should tell you to stay away from it.