Feature Description

I'm working on upgrading to version 15 and after running the migration and starting to investigate the changes required, I noticed that if you don't define a custom theme or import a default one, components' styles will be broken.

When I went with a default theme, I wanted to fix some structural strangeness like this:

Then I noticed that this and other structural styles (like paddings etc...) are defined in a theme file instead of being a part of the core.

Why? Aren't they supposed to be the same? Shouldn't theme be about color and typography?
Am I missing the density here? But even if so, why not have a default styles that can optionally be overwritten by applying a theme?

Use Case

Including (at least) structural styles into the core styles imo would make it clearer and easier to start using the library, since you wouldn't have to learn about the theming (you gotta admit, it's confusing). Also it feels less of a hack to overwrite library's CSS from one source than multiple.