From what I've read a significant contributor to that congestion is routers using too much power. A router in the middle of an 800 ft^2 one bedroom apartment in a dense apartment complex doesn't need anywhere near as much power to cover the whole apartment as does a router at one end of an 2200 ft^2 4 bedroom ranch style house in a suburb.

Out of the box most consumer WiFi routers will be configured for high power and most consumers won't even know that it is something they can change. Even if someone does know about it lowering it will probably make things worse for them unless their neighbors also lower their power.

Maybe consumer WiFi routers should also include some kind of long range low bandwidth communication method, such as LoRa, to find and communicate with surrounding routers to build a map of the routers in a general area (not necessarily a spatial map [1]) and then agree on power levels and channel assignments to avoid interfering.

[1] it would be a map of how they relate by WiFi signal strength rather than how they relate in space. So a two routers that are a couple meters apart but on opposite sides of a wall that nearly completely blocks WiFi radio frequencies would be far apart on the radio map despite being very close together spatially.