Televisions are one of those products that becomes less reliable as you get more expensive. One issue is edge lit LEDs which are run at higher brightness so you can create a thinner television. Televisions typically are more reliable when they are fatter at the back and often can have better sound due to larger speakers. They also typically have better cooling and the larger number of LEDs run much cooler due to their lower light intensity.
True but not relevant for OLED panels as per OP's choice of TV. In OLED each pixel is composed of a cluster of LEDs so emits its own light.
There is no requirement for backlighting unlike LED-backlit LCD panels. Back in the day LCD TVs were backlit with cold cathode tubes so were even thicker.
The panel on our Hisense OLED TV is about 5mm thick including the aluminium casing. However the TV body includes a plastic box of about 40mm depth at the back lower down which houses speakers and electronics.