Well, we need much more on our end than the power of a cellular signal- For instance, one of the support antenna dishes of the Deep Space Network is DSS-42 in Canberra... which is a 70 meter diameter parabolic dish. And the transmit power on our side is in the tens of kilowatts. Literally tens of thousands of times more power needed than a cell phone and directed by a 70 meter dish....
We need that because the dish on the Voyager probes is 'only' 3.7 meters. Still... not a cell phone antenna.
That said, the transmit power of the Voyagers is tiny in comparison to ours and it is closer to that of the cell phone analogy- still more, however, at about 23 watts [1]. So, our end task of receiving that, by the time it gets to us, is damn impressive indeed I think.
[0] https://www.youtube.com/watch?v=FzRP1qdwPKw
[1] https://public.nrao.edu/ask/how-strong-is-the-signal-from-th...