Yeah, with you there, although, if it is to be taken symbolically, …what is being asked of you (us, etc) is to sacrifice all that is most dear to us, and thus it implicitly shows that a man's own first born son is his most prized "thing" of all …
It is your obedience, your TRUST, your loyalty, your allegiance is being tested…
To see that all the things of this world, all the things a human ego clings to… must be put into the proper, TRUE perspective…
Must be abandoned in order to "see God", or to return to the Source.
It's an allegory.
Unfortunately, some people are stupid enough to think in the most brutal, basic, literal terms, and thus through their blindness and misunderstanding can mutate and evolve sorcery and magical thinking.
Which is a whole 'nother story…