I forgot to mention that a stripped down importer bookmarklet does actually exist. Please see here: Install Web Importer bookmarklet
The catch with this is that it doesn’t work on some websites which prevent external scripts from running (BBC Mundo is one such site).
I tried creating an Apple Shortcut which runs this importer bookmarklet code but although it works on some websites it runs into the same issue with external scripts on websites like BBC Mundo. I think it might work if all the code could be included in the Apple Shortcut instead of pulling from the server, but I couldn’t get that to work (perhaps because it’s a lot of code including JQuery and Readability libraries).
I imagine “Get contents of URL” won’t work on pages which use Javascript to dynamically render in the browser.
Anyway, I’m going to leave this for now. Apple Shortcuts feel like a power user feature so probably only a small number would benefit from it and one day I do hope to create an iOS app which will allow adding a Share Sheet action in a more user friendly way.