2017 GTh here.
• Nav volume doesn't adjust with the radio volume. If I've got my music up, you can't hear the nav give directions, but it does dip the sound out, so that's quite annoying.
•*The DRLs on models with the Bi-LED lighting system aren't actually DRLs. They're just the headlights and they stay on all the time whether you switch them off or not. So, having "Automatic" headlights is a joke. Having parking lights is a joke. Having that switch at all (except to turn on the fog lights) is a joke.
•*There's no interior release for the hatch. I drive to secure government buildings a lot, places where they search your car on the way in. They tell you to open your glove box, hood, center console, and trunk without getting out of the car because they have a method for searching cars that takes like 15 seconds and they do it all day. So when I roll up and have to get out to open the trunk (because they can't find the release button because it's hidden) they get all pissy.
• The drive-by-wire gas pedal hinges at the bottom. Every other car I've ever owned has hinged at the top. I'm used to pivoting my heel to go from gas to brake, and doing that means I have to put so much extra force on the gas pedal to push it, it feels like I'm flooring it.
Many of your points are valid and agreed upon by many, especially the window switch complaint, everyone complains about that one. However, I'd like to address the above:
1) For the nav volume, you're right, it doesn't adjust with the radio volume. However, it sounds like you haven't figured out how to adjust it at all; it's independent. You can turn the nav volume way up so it's quite loud. The catch is, it's kinda clunky. You need to wait until it's actually talking to you, and then adjust the volume knob/button.
2) I think what you may be missing here is that the automatic headlights also control the high-beams. (I have the '15 model with bi-xenons so I may be mistaken, but this is how I believe the bi-LEDs should work) In "off" mode, there's no high beams, but pulling the left stalk will give you flash-to-pass. In "auto" mode, pulling the stalk should also give you flash-to-pass, but pushing it forward should put it in auto-high-beam mode, so it'll turn on the high beams when it doesn't see any oncoming headlights or brake lights. In "on" mode (the last setting), it'll let you control the high beams manually. But yeah, I can see why the "off" mode really doesn't make a lot of sense here with the LED highlights also serving as DRLs.
3) There's been lots of complaints about the hatch release. The problem is, can you point to any other hatchback car on the market today that has this mythical interior release? There isn't any. There's been tons of discussions here about this very subject, because Americans keep comparing the hatchback to either 1) sedans or 2) SUVs with automatic liftgates. A hatchback is neither. Hatch doors are very heavy (unlike sedan trunks), and are held up with gas struts instead of torsion rods. There's simply no way to make them open remotely; you could tap into the wires on the hatch-release button and activate that remotely if you want, but it won't help because without lifting the hatch, it'll just re-latch, and the dummies outside still won't be able to lift it open. The only way to "fix" this is to put automatic liftgate openers in, like minivans and SUVs have, but now you need to re-engineer the whole chassis to fit them in.
4) The gas pedal is mounted on the floor because that's how German cars like BMWs are. Race car drivers who drive high-end European cars like BMWs and McLarens do it somehow, and seem to greatly prefer that gas pedal arrangement, so that's what Mazda adopted.