It's funny that web components were already included in Internet Explorer 5 back in 1999! They were called "DHTML Behaviors", but the idea was the same.
Behavior components encapsulated HTML, CSS and script content, and had a .htc ("HTML component") file format so they could be loaded from separate assets:
I guess they didn't see much use in the real world, even though IE had a >90% marketshare for years. That might be a data point in support of the OP's concerns about the usefulness of components.
.htc files were a performance nightmare. They were (mis)used for pre IE8 polyfills - often delivered by ad-networks - and of course downloaded and executed in a synchronous blocking way. .htc maybe were a sane idea, but horribly executed.
Behavior components encapsulated HTML, CSS and script content, and had a .htc ("HTML component") file format so they could be loaded from separate assets:
https://msdn.microsoft.com/en-us/library/bb250408(v=vs.85).a...
I guess they didn't see much use in the real world, even though IE had a >90% marketshare for years. That might be a data point in support of the OP's concerns about the usefulness of components.