sorry, I might be mixing up things/concepts - still new and learning. But isn’t a shortcode in the end a reference to a partial? So I should be able to use the partial for embedding youtube/vimeo etc.?
In a nutshell, shortcodes allow you to use template logic directly in your content. If you’re editing a template, no need to use a shortcode. Whatever code is inside the shortcode, you can likely copy/paste into your template.
but isn’t the philosophy of shortcodes and partials - write once re-use it everywhere? Basically try to avoid copy/paste operations? Why do I have to redefine something, that is already there, instead of just making a call to the built-in functionality?
Sidenote: Where are the built-in shortcodes defined?
No, partials are reusable code for templates, shortcodes are reusable code for content. If your use case allows for reusing code between the, then you will probably figure it out. But most shortcodes and partials do not share code from a practical standpoint. I have no philosophical qualms with that.
So, a shortcode can include partials (which is fairly common), but even if using shortcode templates from “regular templates” is possible, I don’t think it is practical. A shortcode will typically have a different API.