We should analyze, first of all, the axioms. Are we sure we have experienced the "beforelife"?
Imagine that you did something many years ago, but now you don't remember it at all, can we say that you experienced that? You experienced it, however, now you don't remember that, and any affirmation that you make of that experience will be a mere fallacy or supposition, a work of imagination, since you don't remember.
In the same way, can anyone remember his "beforelife"?
We can say that being dead is the same as we were before we were born, it would simply be an assumption, although it is very interesting, the problem is that we don't know how it was, the reality is that we can not remember how everything was before we were born.
From there to many theories, such as those of reincarnation, or those of an eternal cycle, since we can not know how and if there was something behind, the reality is that we are in the same, because it is an incognita both "afterlife" and "beforelife".
Sure, we can say that we did not exist before we were born, but can something appear out of nowhere? Since to say that we did not exist before, and now yes, it is the equivalent to say that, before there was nothing, and suddenly something appeared, and nothing can come out of nothing.
Of course, these are just my thoughts, greetings!