You said that the build quality is poor. It might be a matter of semantics or, based on what you said regarding the responsiveness of the screen, it sounds more like you had a defective unit. In either case, I don't think that your experiences are reflective of what the majority of owners experience. But I am in no way refuting what you experienced. It IS your experience.
I owned a Fire 7 before getting the HD 10. The build quality was fine. My definition of good build quality: The glass was well fit to the body with no gaps. It was very rigid with no flexing. The touch screen was responsive. The screen was bright and evenly lit. There are some who "defend" the iPad against the Fire by claiming that the reason the quality is so high on those inexpensive tablets is because Amazon loses money on the tablet sales but makes it up on the services they charge for. I haven't seen any evidence to back up that claim, but even they acknowledge the Fire's good build quality.
The Fire HD is often viewed as nothing more than a consumption device to consume Amazon services. That is indeed Amazon's intent. But the reason I posted that photo of my HD 10 is because the HD 10 has the potential to be used beyond that. Bluetooth keyboard, Mouse, SD card support, and comprehensive support for USB peripherals (it handled everything that I attached to it) I found that pretty surprising for a device targeted and marketed as a consumption-only device.