Spring IDE is a collection is various features to enhance the regular Eclipse IDE with tooling for building Spring-based applications. While some features of Spring IDE are still under active development and are shipped as part of the all-new Spring Tools 4 for Eclipse distribution (like the Spring Boot Dashboard, the project-specific XML namespace resolution, and the Spring Boot launch support), most of the remaining features are not under active development anymore (like the XML-specific support for Core Spring and various additional Spring projects). Some of those features have been re-implemented as part of the Spring Tools 4 using the architecture of language servers.
We strongly recommend to migrate to the all-new Spring Tools 4 for Eclipse, if Eclipse is your preferred development environment. In case you are missing specific features from the Spring IDE that are not yet part of Spring Tools 4, please file an enhancement request against Spring Tools 4 here: https://github.com/spring-projects/sts4/issues
More details about the previous Spring Tool Suite and installing previous versions
Please find more information about the previous versions of the Spring Tool Suite 3, which contained all the various Spring IDE components, here: https://github.com/spring-projects/toolsuite-distribution/wiki/Spring-Tool-Suite-3