if a baby monitor is interfering with your cordless phone or WiFi, that is probably the least of your problems!
Umm... so what is the bigger problem you are implying? And what exactly can't you agree with? When a lot of 2.4GHz devices are all operating in close proximity (such as apartments in a city) there will be more interference than if those devices are farther apart. It's simple physics.
I know from direct experience that a single 2.4GHz consumer product (such as this one, which BTW does not tell you it uses 2.4GHz video anywhere on or in the box, and only states the much lower frequency of its control channel) can completely swamp WiFi across the width of a suburban house. If there weren't a big yard between us, it would probably knock out my neighbor's WiFi too.