The people who decide bringing new life into this world is unethical will quickly be replaced those who think it _is_ ethical. I understand your reasoning, but "don't have kids" can never be the answer.
It might never become popular but every individual aware of the argument can then choose to reproduce or not (assuming they aren't barred from it for other reasons). In other words, we can't really hide behind the survival of the species as a whole when we consider our own actions and their ramifications.
We know the great mass of humans will carry on as before and there's little we can do to change that, but we are also aware that we have this responsibility that we can act on in our own life. Every person in the position to reproduce has a choice laid out before them. For the majority of us, it's the single most impactful ethical decision we will ever make.
From what perspective are you using the word "quickly" here? From human scales, quickly isn't true as China has been limiting to 1 kid for how long? From cosmological scales, humans barely even existed.
