>This "law" is only for point (or spherical) sources, i.e. those emitting evenly in all direction
We're not talking about lasers and directional antenna here, we're talking about humans using radio communications to talk to each other on Earth over the last 100 years, and whether that's detectable from great distances.
military radar transmissions set up during the Cold War to detect incoming ballistic missiles have the power and frequency characteristics to be detected over hundreds of light-years – and have already broadcast our existence to any aliens within around 60 light-years of the Earth [1]
But never underestimate the power of television:
The most detectable and useful escaping signals arise in a few ultra-powerful military radar systems and in normal television broad-casting. A model including over 2,000 television transmitters is used to demonstrate the wealth of astronomical and cultural information available from a distant observer’s careful monitoring of frequency and intensity variations in individual video carriers (program material is not taken to be detectable). [2][3]
once the Square Kilometer Array is completed in Australia and Africa, it would be able to detect the current TV carrier wave radio leakage at a distance of about fifty lightyears for objects in the southern hemisphere sky [4]
We're not talking about lasers and directional antenna here, we're talking about humans using radio communications to talk to each other on Earth over the last 100 years, and whether that's detectable from great distances.