Is it possible to has have a creator but that creator not to be a god? For example, if we are living inside a simulation created by a software engineer, is that engineer our god?
Does your definition mean the rejection of all spiritual or supernatural beings requires one to become hold views inline with existential nihilism?
If it is revealed to such a world that there are in fact supernatural beings, how does that create meaning and value?
And how do those supernatural beings derive meaning and value; don't they need another level of meta-supernatural beings?
I want everyone to have meaning; I don't want there to be supernatural beings which are kind of slaves to provide me with meaning by their existence, but are themselves starved of meaning since they have nothing more supernatural than themselves to believe in.
One useful definition of meaning is the evolution of possibilities. A situation of no meaning is one which is a dead end in terms of possibilities.
If the universe dies in a heat death, then at that point there are no future possibilities distinct from the current state, and so there is no more meaning.
There might be no permanent meaning; no value that will endure forever, but people can be content with the temporary meaning, in which they enjoy new experiences and explore new possibilities in any endeavor.
Human lives end come to an end on a time scale vastly shorter than the death of the universe, yet people are able to find meaning.
So, I am not tone deaf: I do hear that. Just let's use "atheism" right, too.
But note that someone identifying as an atheist, but with spiritual beliefs, might not be found to actually be an atheist, if their beliefs were examined by hard-line atheists. It is possible that a belief can have the trappings of being free from gods, but when you examine it critically, the entities in that belief can be identified as god-like after all.
Strawman examples:
"I believe everything has a purpose; but there is no such thing as god". Sorry, a purpose requires a being to articulate the purpose and set it into motion. If you mean inherent purpose (rather than a human interpretation which ascribes a non-inherent purpose) you have a god hidden in there.
Or "There is no such thing as god, but the world was clearly created". Oops again. Creation without a creator?