(1/2) I believe in Omnicidism (A similar, but distinct idea is Efilism which is against creating any life, but it can lead to Omnicidism which is why I have mentioned it) which is a moral philosophy where the most ethical course of action is the instant and painless annihilation of all life in the universe with no chance of it coming back. Of course, this is impossible for now but I am arguing it as a thought experiment, not as a pragmatic idea.
I will introduce why I believe in this by starting off with my definition of suffering. Suffering is any negative experience experienced by a sentient being. It is bad because it is everything that is bad. Suffering is good only when it prevents future suffering. Otherwise, nobody enjoys suffering because it is not suffering if it is enjoyed.
Adding onto this point, I would like to introduce Negative Utilitarianism. In this ideology, not creating suffering is valued above creating happiness/pleasure. Hard Negative Utilitarianism is a concept where not creating suffering is the only thing that matters. This relates because omnicidism is against all procreation because all procreation creates suffering. The fact that most people report being happy is irrelevant because we only need to focus on not creating suffering. You are not unethical if you do not give resources to the homeless, but you are if you decide to take resources away from them. Taking someone's life is unethical, but not creating life is not unethical. The logical conclusion of this is to prevent all life from being born, and to prevent all life from being born you must kill all life so that it does not reproduce.
On that note, you may be thinking "According to your philosophy, wouldn't murder be ethical? Shouldn't everyone kill themselves then?" to which I say no to both. Murder is unethical because it inflicts grief-related suffering on those who care about the person who was murdered. Suicide also follows, being a net negative. However, this can lead to unfortunate implications to those unloved. For example, if we kill the homeless, then people would be more stressed about becoming homeless.
Another argument is that procreation is gambling with someone's life without their consent. If you forced someone to go into a room where they would have a 90% chance of winning a large sum of money but 10% chance of getting cancer, most people would be understandably upset at you gambling with their life like that. Why would life be any different? When you give life to someone, you're risking an innocent person developing suicidal depression, being kidnapped and tortured, getting an incurable disease and much more. They may still think that their life was worth living, but why would that make it okay to let someone else suffer as much as they did?
Non-existent people cannot miss or want pleasure. By bringing someone into existence, they become a slave to their instincts, fears, and desires. Wanting to live does not mean life is good, much like wanting to drink does not mean alcoholism is good.
My final argument is that life is generally a negative sum game. It may not look like it for humans, but it is very probable that most animals suffer more in their life than not. If you want a demonstration of this, compare the suffering of an animal being eaten to the pleasure an animal gets from eating it. The suffering is much greater. Not only this, but imagine being a prey animal. Mortal terror is a very common occurrence for these.