There are several devices that will give you much better sound than a Zoom H4n or similarly priced Tascam recorder. I own a Tascam DR-100, it's great for what it is, I've used it and will definitely use it again, but does it have the cleanest preamps out there? Hell no! These things are so compact and try to do so much that you can even listen to the SD card activity interference in some situations! If you know a thing or two about preamps you'll know these recorders' preamps are decent, but far from "professional quality" and perfectly matchable by any camera that tries to. Most of what you pay for is the firmware, card recorder, plugs, headphone amplifier, etc etc, which you already have in any camera anyway!
Devices, not cameras. I'm not saying the Zoom is the best option, it's definitely good enough, as well as other purpose-built devices like it. It's completely r-tarded to be wasting engineering and space on advanced audio for a camera when that cost, that time, that extra potential for issues would be better spent on its true purpose.
Single shooters can attach these compact recorders to their shoe on top.
You actually complain that these compact recorders are trying to do too much yet you want to jam pro-level audio gear into a camera. This conversation is absurd.