Social sharing, interactivity, and reasonable-to-high levels of visual polish were all frequent features presented with raw HTML/CSS a decade ago. If you have a decent designer available to you, some of them can hand you a quality original screen design in an day or less in a PSD/Illustrator/whatever file, and it's possible for most cases to convert it to HTML/CSS from scratch in about the same time (at least, it was for me by the time I'd done a hundred or two of them). Responsive may add time depending on the layout conception. All of this can work pretty much the same today.
If you don't have a good designer and/or design isn't going to distinguish you (or you want the benefits from fitting into widely-present framework styles), a template or framework can make a lot of sense. But that's a different proposition from saying HTML/CSS is a dying path.
Interactivity & Sharing: up to a certain point, interactivity via progressive enhancement costs no more time/effort than application-centric approaches unless you're truly building an application over a hypertext document with some added features. Possibly less. Social sharing is usually a matter of dropping the right widget into a page.
> Forcing them to start with an empty notepad document is like getting someone interested in cooking by making them grow wheat.
It's more like having people start with buying/using their own staples instead of a meal kits or deli meals. The latter can be delicious and convenient, but it doesn't mean the staples aren't a viable path.