I did not make any strange assumption about the aliens
I said :

Suppose that they exist and their level of technology is very high ( of course it must be) , even so it is unlikely that they reached us because of the size of the galaxi , the distances and the speed limit
The only assumptions I made is that the physical laws are valid also for them , thus it make no sense to claim " the may have already overcome such obstacles "


Are you not unaware of Fermi's simulation ?

He took into consideration the foundations of colonies and he came to the conclusion that our galaxies should be crowded with alien colonies and the ether full of radio frequencies
Even nowadays SETI radio telescopes have not yet detected even one signal

Obviuosly it was not his main area of interest

The result of the Drake's equation depend on the value assigned to the parameters which are mere speculations
I have never taken this equation that seriously
However evolutionism is a deterministic theory

if the enviromental conditions are suitable life must evolve

There are 400 bilion galaxies with 400 bilions stars with , may be, 10 planets each
The number of planets can be estimated in :

n = 160.000.000.000.000.000.000.000

It is hard to think that none of them is suitable for life except the earth
Obviously nobody really knows