Easy: there isn’t one.
Life, in all its forms, is just a meaningless accident.
Well at least you recognise that we have a problem currently, and that it needs to be solved. 
As for things not changing, this isn’t factually correct. We don’t live in the same world as fourty years ago. If we were, we in Europe would already be dying from all our infected rivers and lakes, and polluted groundwaters.
Everywhere, there are people trying to change things. Many cities for instance evolve towards a life almost without cars (Copenhagen as an example, many others following suit). There are also a lot of small-scale initiatives to change the way we produce food or other products, away from the classical industrial model.
Some countries produce already a third or more of their energy with ‘clean’ energies (water, solar, thermic, wind), and the trend is upwards. Changes have been made, but the problem is that these changes aren’t happening at a fast enough rate currently.
So, to come back to topic: the problem in order to accelerate the ongoing changes is to fund them more abundantly. And to do this, there is only one way: remove a part of the financial inequality, and take back a part of the money owned by the super-rich and their multinational companies. And before you say that it can’t happen, it has already been done previously, and it will happen again.
Think about Roosevelt, how the mega-trusts at the beginning of the XXth century were broken up. Nobody thought it could happen at the time, and yet… The super-rich will be more and more made aware that too much inequality isn’t in their own interest. For their businesses to prosper, they need a stable and well-functioning society. And that can only happen if they agree to share a good chunk of their wealth for the common good.
If they fail to recognize this, then they or their descendants will eventually end up with their heads on spikes, it’s really as simple as that. That too has already happened in history.
Easy: there isn’t one. Except for football.
You aren’t wrong. Passing on our genetic material is indeed a key component of our existence. One could even argue that we are nothing but mortal vehicles for our genes, who are immortal as long as they find a new vehicle.
We also have natural functions which help life to be perpetuated. For instance: breathing as a purpose. The CO2 we emit by breathing (or farting haha) is vital for all plants on earth. Without the breathing of animals, no plants. On the other hand, without the photosynthesis which converts CO2 in oxygen, there would be no animal nor human being. I find this fascinating: the breath of life going from the plants to the animals and back again, indefinitely.
However, why must these genes be passed on by all means, eh? 
Completely off-topic now, but I’ll tell you what I think is our purpose. Life is all about beauty. The sheer, immanent, sometimes terrifying beauty of existence. I see our role as human beings to recognise it, and to add to it with our own means. You said that the arts, love, compassion etc. is a by-product of passing on our genes, and that it has a meaning as such. I agree with that, but the argument can also be reversed: passing on our genes must happen in order to perpetuate the beauty of life, including love, arts, music.
My personal experience is that the more I manage to recognise this and actively live it and build on it, the more my life becomes one with an actual purpose.
I really don’t get the appeal. Why do so many people support such an obviously narcissistic egomaniac?
Shoot all the billionaires and the world would start to be a better place.
Because people are fuckwits.
First they came for the billionaires, then they came for the millionaires… 
various reasons, but a lot of it is probably because he is seen as anti establishment. Obviously very clever and can get things done. Also good at using media to promote himself.
Personally, I’m not much of a fan.
But he’s such an unpleasant dick.
Reminds me of someone actually 
To be honest, if I have to explain you’ll never get it.
Great idea, kill all the wealth creators.
Yes because they obviously create the wealth. Not the actual innovators, engineers, producers…
That’s just a cop out as you well know.
He is a dick.
At the same time the world needs those that will push boundaries, take risks, and drive towards a vision.
Some of the best scientists, engineers etc work for NASA. But they are now outsourcing to SpaceX. From Tesla batteries to cars these are high risk disruptive technology development. A big role making these mainstream.
As a man I dislike him, but he is one of the most men of our generation.
It’s not. If you can’t see what Musk has done positively given that everything he does is massively obvious and in the media glare then there’s just no point me trying. Did you watch SpaceX launch another 4 people to the ISS earlier? Doubt it. I did.
The NASA point I think is one entirely about the whole right-wing narrative of cutting back government.
If the US government’s research capabilities hadn’t been cut back so much, who’s to say all these wouldn’t have been achieved without that narcissistic twat?