I haven’t experienced visible “code” when disabling Elementor and viewing the default content. It appears that it leaves text/images and embeds for the most part, essentially un-styled content.
With some clever css, one could target the unique “wp-content” version with some styling that would not interfere with an “active” Elementor loaded page, but would act as the “clean” fall-back version if should ever the plugin become disabled. The trade off is extra time to do this and a little extra bloat in your css.
The other glaring problem here is that you don’t get any choice in picking and choosing what “wp content” is saved in the standard post editor vs what gets cut out when the plugin is disabled. Each widget is handled differently and some of which may not render anything at all in absence of the plugin. I have not investigated this personally but at any time one can see what exactly would be shown by simply choosing the use the default wp editor when editing a post/page via back end.
I agree, it would be cool if a page builder was developed to be more of a portable tool that one would use to create site content but leave no dependency except that of which is needed for the specific content created. How would it do this though?
It would have to be smart in it’s approach, maybe bundling the created content along with proper css/js and php libraries nested and nicely organized within one’s child theme making it also completely portable outside of a db grab.
That would be the ultimate developers tool while still being friendly to the end consumer providing the easy-to-learn/use visual front end designer.