You are assuming that any kind of "objective morality" should overrule any moral system constructed by humans.

This is, IMO, a mistaken assumption to take. Let's say that there is a purpose in life, or that there's some kind of moral out there which is somehow, in some way, objective.

The essential question many do not ask themselves: what if there is a some objective morality? What if there is a purpose with life, and we discover it?

The moment you find the slightest level of disagreement with morals or purpose, you may dismiss them with no repercussions whatsoever - there is nothing outside the human realm that enforces or inspires the grand idea of such things, beyond our own need to find a place we belong to, and people spreading around the futile idea that there really is something greater out there than all of us that we must know about.

Furthermore, it is very easy to find disagreement - just ask what decision should be made in extreme situations and you are guaranteed to find disagreement. But surely, it would seem absurd to disagree with "objective morality"? If there is a purpose with life, and we don't like it, why should we even care about this objective purpose?

Let's say the purpose is to just enjoy yourself, in all kinds of ways. Well, there are many ways to go about that goal - you can act very rationally, or with complete disregard for others, prioritize a few you care about, prioritize yourself above others generally... but disagreement is easily found even with this purpose. Some are not content with this suggestion, and so, it is easily dismissed and should never be regarded as a candidate for "the meaning of life".

Let's say that we could understand "objective morality". That is no guarantee for agreement, for human beings are not completely rational. As such, objective morality is really just another moral compass among many. If we can't understand objective morality, then that's not exactly a problem either.