If all life evaporated from planet Earth tomorrow never to return, where is the value or meaning of anything you did or said or learned or contributed? It ceases to exist. It was all for naught. That is the point theists are making when they say that life without God is meaningless and without purpose. Whatever meaning or purpose you have as a human being is temporal. At some point, it will evaporate into nothing.
I find the importance you (and other believers) place on meaning rather perplexing. It seems to be a requirement without which life would be insufferable.
We humans can say "Oh gosh, life has to have meaning, so I'll give it some..." I can see that, though it is not one of my higher priorities. But we don't even have a good definition of what "meaning" is, in this context, so how can it be so important? Why, if meaning is such a central part of the god stuff, can't a believer tell us in a phrase or two why that is the case? Why can't any two given believers give us identical versions of what "meaning" really is?
Its made up. Lots of human things are made up. Including truth, something none of us can know. We can inch our way to "truthiness" in some areas, but outright truth is not available. So right now on the forum we have one believer in one thread talking about how important truth is, and we have you here talking about how important meaning is, and neither of you can describe it in any useful way. You can't even tell us why it is important, other to say that life would be meaningless without meaning.
Life doesn't have a meaning. It has a biological purpose, to procreate and continue the species, and life in general. It has functions, such as to fill biological niches and provide food for other critters once we die. It includes processes, like eating and walking, and it includes biological imperatives, which most of us think we ignore. But there are no genes for meaning, no cells for meaning, no needs for meaning.
A lot of us make up meanings. Which explains in part why it is so hard to define them for others. Because in your case, you are trying to tell us you meaning is more relevant that whatever it is that we atheists have made up.
I understand the concept. I accept that it is faulty. I don't understand why some insist that it is a requirement.
And why the "fruitlessness" of it all once life ends? Why look at it that way? Why is that in any way relevant? If we choose to assign value (not meaning) to our lives as we live, and if some of us also take into consideration future generations as we live this life, that is about all anyone can hope for. We don't have the biology to do much else. We don't genetic rules to follow that require that we consider the far future. We all know that life won't go continue on this planet forever. But fretting about what will happen when we're gone (in the philosophical sense) is of no use. The American Indians were kind enough to consider the next seven generations when they made major decisions about their environment. We modern humans tend to consider only what the price of gas will be this weekend, and that only if we're taking a trip. Most of us have no long view of anything other than our favorite TV shows, and we suffer interminably when we find out that the next Harry Potter movie will not be released for another eight months. So why this one, and only one, concern about the future? That our lives have meaning?
Life has no meaning. Other than what we self-assign for our own convenience. Live with it. There is no way to die with it.