Is the purpose of a fire to require more fuel? Having fuel is a precondition of having a fire, and it continuing to have fuel is a precondition of to remain a subject for discussion. Similarly for survival - it's a precondition, we had to have that bias to have got here, to have evolved. But we know humans can & do choose not to survive - & sometimes we call that the summit of the moral life, sacrifice for others. In antenatalism & efilism people have gone further, suggesting creating new life is immoral, because it causes suffering - net-unhappiness would make life unjustifiable, if you make happiness it's purpose.
Happiness is not a thing. Utilitarianism wrestled with this, trying to quantify it with various types of ranked pleasures, hedonic calculus, and so on. It leads to many problems & paradoxes, like a 'super maximiser' experiencing sublime states getting to exploit everyone else (of course, we do this to animals, and have done to slaves, which should make us consider this carefully..). Peter Singer has shown a kind of capacities methodology, can help us be consistent in approaching ethical dilemmas, but many don't like where that leads in some cases like around disability.
Even purely as an individual, saying our purpose or meaning is happiness just substitutes words. We say whatever we decide to do or find meaningful, we do so for 'happiness'. And we can do no other - even suicide has to be pictured as seeking a kind of happiness in ending suffering. It's a tautology, to say we seek happiness, if happiness is pictured as just, the necessary result of getting whatever we do in fact decide to seek. Happiness as usually pictured is a compass direction, it can evaluate a kind of gradient between directions you could go in, but not why. This is Hume's is vs ought distinction again, however precisely you lay out how things are, including exactly why someone else should choose x, for 'happiness', it will be down to them, their impulses. And we say, as long as they can justify what they did in a court of law, and among their friends, and to themselves, that wasn't immoral. Even, if they all think it was crazy, self-destructive, inconsistent, etc.
Aristotle had an explicitly open-ended idea of happiness in eudaimonia, 'human flourishing'. Both fulfilling our natures, and reaching beyond them to develop what that is. If we explicitly set happiness in a wider understanding of human nature, eg what a wise and virtuous life is, we can say true happiness is our goal it will be fulfilled by living up to x understanding of life. But that will always be open to debate, & question, and a subjective personal journey to defining it. What is your 'flourishing'? How do you understand wise & virtuous?
However you square it, survival and happiness are not enough, even to really get started on how to be moral. We need a big picture about why. We need to look at actual behaviour. And we need personal engagement with these kinds of considerations, to find personally satisfying answers.
In short, we still need philosophy!