The basic idea to meaning (as in "meaning of life") is that it is indeed something in your mind (or some process in your brain, it doesn't make much difference here I think). How it get there is certainly interesting but that's not what most people are interested in when talking about the meaning of life.
What seems to matter here is what, if anything, changed as a result of our age becoming allegedly more materialistic. The way meaning works would not have changed, obviously, even if our views about the issue did, but the meaning we see in life may have. Specifically, if your materialist, you may want to drop any religious notion from the meaning you see in life.
So, what remains? Personally, I don't see that's any problem. I'm not religious, never have been, and I always seemed to have a longing to find something meaningful to do in life, and as things stand, my hands are full today. So my interpretation of the issue raised in this thread is that there's a confusion between the issue of what should be our view of the nature of meaning and the question of what kind of meaning you can reasonably (or rationally) have nowadays.
Sure, there is a restriction of sorts, but dropping God from the equation shouldn't be so difficult. Finding something meaningful to do can be but there's still a wide range of choices and life is a long time to find meaning to it once you stop being confused about what meaning is. Although finding a purpose in life is not mandatory I think it does help and finding a meaning to life will help you find a purpose. And I think that's a good idea. It's good for how you feel about yourself, which seems good enough for me although I can see how one can go to far in this respect.
EB
I've been thinking about this thread over the last few weeks, and the above comment.
I'd say that where materialism comes into play is that it's an ontological shift from religious traditions, which sets a new 'framework' in which we understand ourselves and our lives.
For thousands of years people believed they had souls, and were following rules for entry into heaven. That, amongst some earthly concerns that are still present today, defined what living meant to people. Today many people don't have a belief, but the knowledge that existence is fundamentally impermanent and without objective meaning.
So that knowledge sets an entirely new framework in which to approach our lives. If we know that we are impermanent, and that in the grand scheme of things, not much we do really matters, how do we come to terms with and find joy in our lives?
If I'm honest, this is something I grapple with quite a lot. I view the world as essentially unreal, and most things that happen as not really important or meaningful. But I have to live my life despite this knowledge.
So given that situation: how does one thrive and not just give up and become an alcoholic?