Accurately & skillfully communicating research and results does not completely overlap the Venn diagram skill set of "excellent researcher". Research skills do not equate to communication skills.
Postdocs are no more likely to have their Venn diagrams overlap significantly.
But in any case, journals don't do any semantic editing on articles, so the whole point is moot: anyone can be an editor as long as they can typeset and maybe spot typos there and there, and neither communication nor research skill is required for that.
a journal will never edit the text beyond typos. their editorials are written from other peers for free. What copy editing?
Take two scientific researcher of the same discipline & scientific skill level, and one of them might be a very poor communicator. Multiple levels of the editorial process addressed those issues, copy editing included.
Changes were not made without the author's approval: They were edited, proofs sent to the author, who signed off, or declined some changes while adding others. It would then be reviewed by the publisher's editors again, and if all went well a final proof was sent out for a final sign off.
I'm not sure why you doubt this sort of thing: I lived in that world, on the tech side of a small/medium scientific publisher, and saw it all happen & built some of the systems that facilitated the process. It wasn't wasted effort: margins weren't very big and where I worked they would have been happy to get rid of a few staffers if the process didn't require them.
If you published an article through a reasonably sized publisher in a somewhat well-known, did you different experience? If so, then either the practices vary greatly among different publishers, or practices have changed a lot since the early 00's (which may very well be the case)
It also depends on the author guidelines of each journal. Nature group e.g. has requirements about when your subscripts should be in italics. And i think sometimes they prettify images. I don't care about those things, and it doesnt change a thing about the impact of 99% of papers. Most authors submit great quality manuscripts anyway, judging from what i 've reviewed. In fact i m pretty sure i m doing more copyediting and suggestions while reviewing than any of the paid editors.
Another thing is, a ton of effort is wasted in reformatting (and sometimes rewriting) a paper to resubmit to another journal. Publishing is definitely a wasteful process.
There are always publishing costs, but it would be cheaper to set up a public utility for proofreading and uploading papers rather than the current situation
Certain things would get edited automatically without signoff, but only if they were needed to conform to the style guide: some of that was set by the publisher, some by the journal editor.
Copy editing is about a lot more than fluff. Accurately & skillfully communicating research and results does not completely overlap the Venn diagram skill set of "excellent researcher". Research skills do not equate to communication skills.
Typesetting is a little more complex than character format, but you're right, especially in these days with better tools, it's not nearly as labor intensive as it used to be, though still absolutely necessary if the journal is physically printed. Much much simpler if it's online only.
Many journals are still printed and archived especially by libraries, so those logistics are still a factor, and there is a fixed amount of labor required if it's 100 copies are 10,000. After the 100, the required work is incremental.
Digital absolutely has logistics involved as well: building and maintaining a platform isn't free, BUT:
I would wholeheartedly agree that the financial models here are broken and outrageous. Even considering the publishing work I mentioned, whether we disagree on the scope or not, better tools have made that work significantly easier. Scalable digital platforms are also much more of a known quantity and cheaper: inexpensive turn key solutions exist that could be scaled with fairly mundane tech skills. In every way I can think of, the costs associated with turning a raw article fresh from the authors into a polished publication should be much much cheaper.