alt Hacker NewsSpring and JEE (or Quarkus) are very similar, from the viewpoint of an application developer both have the same JAX-RS REST and Hibernate/JPA API's.
IMO the kind of person who only knows Spring and doesn't understand modern JEE is exactly the kind of person you don't want to recruit.
Spring won. Why would anyone want to learn the standard aside from it being a standard that few people use? Spring itself is a wildly adopted standard. It is a semi open standard in that anyone can use it freely, but in that it's not supposed to be implemented by others.
The same is true for Micronaught or Quarkus. Learn the frameworks. But they are not a new open standard.