Something to consider. No alternatives actually propose an objective good either. And why does it matter anyway?

I'm a moral realist. Everyone seems to advocate that some things are properly basic, I think morality is one of those things.

Can't argue against the first point, that distinction is probably true. But contra "hard to locate": Take vision. Suppose you see a cat. Your vision is subjective in a sense... but there's a pretty strong correlation to there actually being a cat.

In fact, all of our senses work like that. So it would be surprising if this other felt sense isn't also usually, approximately, but correctly, homing in on objective good.

Are there times when what we perceive to be true really is rarely the actual truth? Absolutely -- in deeply abstracted thinking, and over highly complex domains. That seems to me to be more of an argument against trusting the complicated chains of logic that lead one to deny the evidence of their moral senses, though. I've made enough "trivial" mistakes in math class that led to a totally wrong conclusion to be skeptical, and that was back when I could check the right answer with Wolfram|Alpha.

(My own deeply abstracted thinking suggests that your moral intuition homes in on objective good similarly to how the processes of markets home in on Pareto efficiency. See how silly that sounds? And yet I can't shake it. It's like making up a conspiracy theory to explain why water is wet!)