Many people take it as a given that positive experiences have intrinsic value, but I don't think the matter is as clear-cut. So here I present a simple experiment which you can try if you are in the mood for listening to music.
Experiment: Listen to some music you like. After a while, mute the music. Alternate between silence and music while trying to appreciate how each feels.
When I mute the music, there is a lingering freedom from what I like to call the "heaviness of being"—basically any pain, unease or listlessness that I may otherwise feel. Turning the music back on definitely adds an enjoyable or gripping quality to the experience. But when I mute it, I don't really get the sense that the experience has become worse, and yet I don't find the peaceful silence better than neutral. This would seem to imply that listening to music is at best neutral.
To be clear, experiences can be impactful and leave a memory associated with meaning and value. Some event can cause me to feel deep sadness and still have this effect, even though I would hardly consider the moment-to-moment experience positive. And my aim here was precisely to call into question the intrinsic value of pleasure, its value when experienced for its own sake. I am curious about your thoughts if you tried the experiment!
Depends what you mean by "moral realism."
I consider myself a moral anti-realist, but I would flag that my anti-realism is not the same as saying "anything goes." Maybe the best way to describe my anti-realism to a person who thinks about morality in a realist way is something like this:
"Okay, if you want to talk that way, we can say there is a moral reality, in a sense. But it's not a very far-reaching one, at least as far as the widely-compelling features of the reality are concerned. Aside from a small number of uncontroversial moral statements like 'all else equal, more suffering is worse than less suffering,' much of morality is under-defined. That means that several positions on morality are equally defensible. That's why I personally call it anti-realism: because there's not one single correct answer."
See section 2 of my post here for more thoughts on that way of defining moral realism. And here's Luke Muehlhauser saying a similar thing.