You say that there is a limit to what can be parsed easily. But there is no such objective limit. Why do people continue to read such writers as James Joyce and Henry James? Obviously some readers do parse them and enjoy doing so. Of course fiction is not the same as non-fiction.
Nonetheless not all readers want or enjoy non-fiction writing that sacrifices nuance for simplicity. Sometimes, in fact most times from what I can tell, writing is so pared down, so simple, as to not have much substance to it. Obviously this is partially subjective. What is richly complex and rewarding to one reader is muddled and confusing to another. Every author needs to make a choice as to just who their audience is.
But there is no reason that an author needs to write for the lowest common denominator. That may be your suggestion but there's no reason that anyone else need agree with it.
I realize that you said you were writing with the good intention of helping the author be more effective in reaching his audience and I don't want to question that.
My argument is that I think that you are wrong in being so uncompromising in your idea of what is good and clear writing. Entangled clauses can be both better for explaining a subject and more enjoyable reading for the right audience.
I've spent a lot of time over the last month reading legal documents. They are incredibly complex and I'm only reading them because they refer to the company I work for. It is difficult reading. But as I've read them I've understood that their seeming complexity is really just an attempt to put very complex thoughts into precise, language. When I was done I admired the language used even though it had been a pain to understand it. But that's the value of language: it can help explain complicated subjects.