Existential nihilism does not imply epistemological or moral relativism, nor does ontological contingency imply everything is random. Sure, there is no piece of empirical knowledge that would say anything about whether or not the universe has meaning, there is however empirical knowledge of true congingency at the quantum level and a priori knowledge against the universe having a meaning. And nihilism is far from being mainstream in any form.
Arguments at the quantum level can just as easily (I would argue more easily) be used to argue for theism as I have done upthread.
Quantum Mechanics is not simply a mechanism for guessing things. It offers us a deep insight that the world is not as it appears to our senses. It is quantum mechanics that leads us to the conclusion that we may actually be living in a
Holographic Universe. The idea the the the world around us indeed the entire universe is simply the projection of a deeper reality.
In his essay
The Universe Anonymint draws our attention to the the holographic principle. Specifically the fascinating notion that when you combine the the holographic principle with the thermodynamic quantities of heat and mechanical work
it is relatively straightforward to derive Newtons classical equation of gravity.
These ideas are difficult to grasp and at this stage they remain theoretical physics. However, there are a growing number of scientist who are taking them very seriously.
Below is a simple but nice introductory video on the topic... I recommend it to anyone who has difficulty accepting the possibility of a deeper fundamental truth and reality.
https://www.youtube.com/watch?v=lMBt_yfGKpU(part I only)
I have argued against atheism on three axes.
1) Metaphysically because the choice (in isolation) voids the existing moral structure rendering the decision itself morally incoherent.
2) Biologically because a sound moral structure is necessary for a healthy life and rejecting traditional structures appears to reduce health, happiness, and fertility.
3) Anthropologically because religion is a critical and perhaps primary mechanism for overcoming our species-specific upper limit to group size which is set by purely cognitive constraints.
While I would concede that nihilism is internally metaphysically coherent in that it is impossible to prove nihilism is false. It is likewise impossible to prove theism is false. My criticisms of atheism, however, do extend to nihilism.
You argued above that nihilism allows one to form a positive doctrine for re-evaluate of ones values and that the end of tradition that produces the possibility of new things to come. However, there is no reason to think the goals of progress and improving our value system and cannot be achieved from a framework of theism. With this in mind why choose a philosophical belief that is potentially unhealthy and detrimental to the progress we have made so far?