Explain to me how the MLA or APA rules for formatting citations are any different? “When it’s a periodical, you put this part in bold and that part in italics, but when it’s an entry in a journal…” Surely there’s a way to do this in plaintext with the rule of “list things about your source until you’re confident someone else can look it up.”

I'm still a bit puzzled why we can't just have various headings in the bibliography, if you want to make it absolutely unambiguous what sort of document you're referencing? Sure, your average Joe on the street might not know how to use a DOI to find a journal article, or an ISBN for a book, but what's the issue with something like this below?

Books

Cite your stuff here with all pertinent information.

Periodicals

See above

Journals

...

Films

etc.

It may not be as elegant and information dense as whatever style manual your field uses with placement and formatting of the information, but it's pretty clear what is what without needing to whip up a whole style manual that will be entirely unknown to anyone outside of your own field of study.

Then again, I'm quite firmly of the opinion that any style manual that advocates in-text citations is an abomination that deserves to have said manuals gathered up and burned, and their creators and proponents sent to re-education camps until they learn the error of their ways and admit the superiority of footnotes or end notes for readability, while maintaining ease of checking references. Personally, I favor footnotes to avoid having to flip back and forth, but I'm also a fan of end notes when there is any further commentary provided on the citation that is useful to know, but would be disruptive to the main text of the document.