Jenkins plugins frequently use libraries for common tasks. HTTP communications are often done with the apache-httpcomponents library. YAML parsing is often done with snakeyaml. Bouncycastle is used to provide encryption. AWS SDK libraries are used for AWS access. Google APIs client library is used for Google Cloud Platform access.
Many of those dependencies can be replaced by dependencies on a Jenkins API plugin that provides the same API for multiple plugins. When an API library dependency is replaced with a plugin dependency, the size of the plugin hpi file decreases, and the consistency of using the same library version throughout Jenkins will help reliability.
Bouncycastle API
Jackson 2 API
Trilead API
SnakeYAML API
JQuery3 API
Bootstrap4 API
OkHttp API
JSON Web Token API
Caffeine API
Bootstrap 5 API
H2 API
Google APIs Client Library
AWS SDK APIs
Font Awesome API
DataTables.net API
Kubernetes client API