[Serious] What is goodness?

[The Grand Nudger]

That would be too restrictive to cover alot of our day to day experience, where we notice that the things we want are very capable of harming us, or of harming others.

Not necessarily. In the first case it could just be that a past desire violated a future desire and in the second case it could just be that we don't desire the same thing as the other person.

I'm not sure what you mean by not necessarily, here.  We do find that the things we desire can hurt us, and hurt others.  That's why a thing can be harm™ even when that thing is wanted.  Isn't that the question you asked?  How a realist might see limiting harm to the unwanted?

One desire can be bad for another desire and this doesn't have to lead to all desires being equal and no desires being good or bad.

Why?

Because some desires are stronger than others. And, hence, some violations of desires are stronger than others.

There's big bad and little bad, but in a desire based system all violations of desire would be some value of bad, because desire is the good or bad making property.  In a desire based system, the fact that Jane does not want an education and actively desires to avoid being educated is morally relevant. In a realist system, not so much. Jane will be compelled to receive an education. In all likelihood, Janes desires will be manipulated to achieve that end.

There will always be some point at which an ethical subjectivist has to throw their hands in the air and give up whatever moral stake they've claimed as insupportable in the face of desire. A realist is under no such obligation. To a subjectivist, the statement "x is wrong" actually refers to some fact of y, the subject. Which is to say that moral statements purport to report facts, but do not report those facts they allege. "X is wrong" is not true, but a euphemism for "y feels a certain way about x". That statement may be true, y may feel a certain way about x - and it may be the case that our moral intuitions are powerfully informed by those feelings. We desire some things more than others and as such y may feel more strongly about one x than another.

The main issue with subjectivism, from an objectivists pov, and particularly with regard to our moral intuitions, is that it necessarily produces incoherent moral states and statements*. A single x, or a set of x's all qualitatively interchangeable can be in multiple simultaneous positions of rightness and wrongness, truth and falsehood, depending on the subject. Helping your neighbor, for example, can be good and bad at once, and is potentially equal to skullfucking their children. Skullfucking their children may be even better than helping them, if the skullfucking is desired and the help is not.

That doesn't seem to be an accurate description of the moral field - but it's an inescapable consequence of subjective moral grounding.

*Mind, as before, this isn't to say that the system is incoherent. It doesn't produce these statements by accident or because it was improperly formed, but because they follow and are alleged to be true representations of the disparate and conflicting nature of subjective agency, which is contended to be the ground of moral value. The comment goes to explain why a moral objectivist cannot accept subjectivist ethics as facts of the matter being discussed, not which (between the two) have it right.