Spring Boot continues to be the most widely adopted framework for new enterprise projects due to its comprehensive feature set, massive community, and seamless integration capabilities. It represents the safe, scalable, and productive choice for a majority of use cases.

Choose Micronaut or Quarkus when your project has specific, stringent requirements for fast startup times and low memory footprint. This is critical for microservices architectures (where rapid scaling is needed) and especially for serverless functions. If you are building a more traditional monolithic or modular monolith application, Spring Boot remains excellent.

Absolutely. While NoSQL databases have their place, relational databases remain the backbone of enterprise data storage. Hibernate continues to evolve, with Hibernate Reactive providing support for non-blocking database drivers, bridging the gap between traditional ORM and reactive systems.

Vaadin is an excellent choice in this scenario. It allows your team to build the entire web interface using pure Java, leveraging their existing skills without needing to learn JavaScript frameworks. This can drastically reduce development time and complexity for data-intensive internal applications.

For a fast-moving startup, Spring Boot or Dropwizard are fantastic choices. Spring Boot provides a richer ecosystem for future growth, while Dropwizard offers a simpler, more focused toolkit for getting a high-performance REST API running with minimal overhead. The choice depends on the anticipated complexity of the business logic.