You folks can live your lives without purpose if you wish. I have things to do.
I have a purpose. Be happy. Safe. Have fun. Well fed. Healthy.
Humanity has a purpose too. But they might say "keep the human race alive as long as possible". Like, this planet isn't going to be habitable forever so maybe we need to send people out into the universe to find new planets. That goal serves humanities purpose. To continue to live for as long as possible.
The more I think about it, my purpose is just the same as humanities. Only I have no say in if we continue on as a species. That would be politicians and scientists. Humanity should have a weapon that can take out an asteroid. This is not a concern of mine.
And the planet will be fine when humans are all gone. When that day comes, what was our purpose again? If there were martians at one time, what was their purpose? Probably the same as mine. Food, comfort, happiness, safety, survival, etc