Defining morality as “good and bad have been defined by us as a result of our species development.” under the umbrella of subjective morality still doesn't give you any objective authority because it's your opinion that this should be how morality is measured. Under the umbrella of subjective morality I could just disagree with you and my disagreement would be equal to your opinion because it's just opinion under the umbrella of subjective morality.

Now if you were to say something along the lines of "Under the umbrella of subjective morality, there's no good or bad in a factual sense, it's all opinionated, and in my opinion people will naturally learn from history and human development beneficial ways to act. These behavioral patterns they learn are not good or bad because morality is subjective, but people will be more likely to fall into these patterns if they value their wellbeing."

Then I don't think I'd have an issue agreeing with you.