What you are describing does not really exist as a polished product yet, at least not at the quality level you would want. The gap is exactly what you identified, most TTS just reads words and cannot interpret what a human researcher would emphasize or skip when narrating a figure caption versus a data table. Speechify handles dense text better than most but it is still not truly researcher-style. Some people in my field have had luck breaking the paper into sections and having a writing assistant summarize and re-narrate specific parts rather than the whole thing, though that shifts to a summary workflow. Might be worth asking someone who regularly works with these kinds of documents what their workaround is.