Can Laptop Cooler or AV Cooler Degrade WiFi Signal??

Wanted to also add that it is common for many TVs, including high end ones, to have weaker than expected WiFi signals. This is due to the way they are built. The entire OLED panel (also applied to LCD panels), can be treated as an RF shield since the backing will be metal. Furthermore, with a thin bezel being a major selling point, there is no room to move a WiFi antenna into the bezel like you would see on a laptop, The end result is often a basic PIFA antenna near the middle of the back part of the TV that will likely end up mounted on a wall.

For WiFi router itself, while a metal laptop cooling stand will not block signals unless the client device is in a room directly below where the WiFi router is located. If there is a lot of metal around the router, then it can wreak havoc on the beamforming capabilities of the WiFi radios in it, which can impact the throughput at longer distances.

Edit: Also agreed on the additional cooling, lower temperatures will prolong the life of the product.
For Netgear devices, it seems they monitor the temperature of the SOC as well as each WiFi radio and if any exceed a temperature set in the firmware (unclear which specific temperature they specified), then the cooling fan will turn on.
Aside from that unlike enterprise or rack mount equipment with fans, a consumer focused device with a fan will likely prioritize noise levels over maintaining the lowest possible temperatures.