As a follow-up of #22171, the Spring Framework reference documentation introduction would probably need some rewrite to be more up to date, useful for modern Spring Boot applications, less XML specific and adapted to separate the global concepts from the various ways to define beans (JavaConfig (and its Kotlin variant), XML, functional (via Java API or Kotlin DSL), Groovy).

The IoC Container section contains various places that likely deserves an update, for example (not extensive):

• Container Overview contains an old looking diagram and is too XML centric
• Basic Concepts: @Bean and @Configuration contains a "Full @Configuration vs “lite” @Bean mode?" that may deserve an update.
• Annotation-based Container Configuration section and its "Are annotations better than XML for configuring Spring?" block could also likely be updated.