Browser vendors are (or should be) managing the abstractions for their own needs, with developer needs expected to be met by framework/library developers.
Who says web components are meant for use directly by the developer? Maybe they're primarily meant for the browser developers (those who build browser features), not for use directly by web app developers.
Who says web components are meant for use directly by the developer? Maybe they're primarily meant for the browser developers (those who build browser features), not for use directly by web app developers.