The beauty of the Star Trek universe is that people have the capability to define themselves what is meaningful to them and pursue it without having to worry about if they will be able to afford to feed, clothe, and house themselves. For some people, that might be nothing but seeing how many other people they can fuck. I believe for a lot more people, that meaning will come from creative or scientific endeavors.
I'm sorry, but you have some sort of noble-savage view of human beings, or a view that supposes the existence of a soul (i.e a view based on philosophy or religion).
LOL. There aren't enough LOLs in the world for this sentence.
If there really was such a thing as "post-scarcity", or if it were even physically possible, we would still be just another species of animal. We would still be nothing more than biological organisms following our perceived self interest.
Nanotechnology research aims at this very goal with our very biology as proof of concept showing that atomically precise manufacturing is possible, and I believe it's just a matter of when, not if. So we're animals. So what? You think that we're constrained by biology to have no other interests than eating and fucking?
The number of people who would risk their lives for some "meaningful" reason - when there was no material one - in deep space for no material benefit would be in the fraction of single digits.
These people would probably disagree. Thankfully, not everyone has the same outlook on life as you do.