The problem with that is this:
The set of planets with life = 1.
The set of known planets without life as we know it is far more numerous and grows more numerous as we discover more planets.
There’s a far stronger argument that we are the only planet in the Universe with life so far.
Oh I hope we continue to search. I also hope we expand our definition of “life”. [I have some ideas there but they’re nothing novel]. But the mediocrity principle strikes me as a weak argument.