I can only speak for myself, but I was lucky to be exposed to Spring Boot back in the v1.5 days after spending a few years creating Java programs without any framework. No XML at all, configuration by code, and opinionated default configuration that covers most use cases.

The learning curve was not that hard, and I got comfortable with it.

In contrast, I find React, Next.js and other frameworks more complex, and it takes a lot longer to be comfortable