So, just for the heck of it I actually looked at some of the issues you reported before, and I found this:
Ok, so first of all when I set mine to 0% it's definitely dimmed. Like, in a dark room it's usable, outside impossible. So if your phone was "blindingly bright" at 0% then there's something wrong with it. I have no idea what, but something isn't working the way it should.
Secondly, I've had the slider available since day-1. I just pull down the whateveritscalled from the top, press and hold the screen brightness tile, and it takes me to the "Display" page of the settings. At the very top is a slider that adjusts level from 0 to max. So, again, I don't know what's going on with your phone, but if you've done a minimal bit of research on such a basic setting you'd have seen it was available, and if you did and can't find it, then something is very, very wrong with your phone.
Incidentally, long-pressing on any of the tiles/buttons takes you to the respective settings-entry for that function. I have the Wi-Fi "tile" there and press-holding it takes me to the "Wi-Fi" page in settings. Easy and convenient, and actually intuitive.
So, none of the above is meant to criticize you, just point out that you either got a spectacular dud of a phone, or you inadvertently did something to it that damaged it, or you're misunderstanding how parts of the phone is used. When users miss features or misunderstand functionality or get on the fast ring without disclosing it or some other way end up with a "non-official" setup and then subsequently post their frustrating experiences then it all adds up to an image of a basically disastrous phone. I'm not saying I don't find some omissions bizarre, or some issues annoying, but the complaints I see really make me suspicious. It can't possibly be the case that so many users have experiences that are truly as bad as the words they use and I don't even have half the issues they describe. It just makes little sense to me.