I see things slightly differently.
Happiness, suffering, etc., function as internal estimators of goal-met-ness. Like a variable in a computer program that indicates how you’re doing. Hence, trying to optimize happiness directly runs the risk of finding ways to change the value of the variable without the corresponding real-world things the variable is trying to track. So far, so good.
But! That doesn’t mean that happiness can’t also be a thing we care about. If I can arrange for someone’s goals to be 50% met and for them to feel either as if they’re 40% met or as if they’re 60% met, I probably choose the latter; people like feeling as if their goals are met, and I insist that it’s perfectly reasonable for me to care about that as well as about their actual goals. For that matter, if someone has goals I find terrible, I may actually prefer their goals to go unmet but for them still to be happy.
I apply the same to myself—within reason, I would prefer my happiness to overestimate rather than underestimate how well my goals are being met—but obviously treating happiness as a goal is more dangerous there because the risk of getting seriously decoupled from my goals is greater. (I think.)
I don’t think it’s necessary to see nonexistence as neutral in order to prefer (in some cases, perhaps only very extreme ones) nonexistence to existence-with-great-suffering. Suffering is unpleasant. People hate it and strive to avoid it. Yes, the underlying reason for that is because this helps them achieve other goals, but I am not obliged to care only about the underlying reason. (Just as I’m not obliged to regard sex as existing only for the sake of procreation.)
I don’t know for sure whether we’re really disagreeing. Perhaps that’s a question with no definite answer; the question’s about where best to draw the boundary of an only-vaguely-defined term. But it seems like you’re saying “goal-thinking must only be concerned with goals that don’t involve people’s happiness” and I’m saying I think that’s a mistake and that the fundamental distinction is between doing something as part of a happiness-maximizing process and recognizing the layer of indirection in that and aiming at goals we can see other reasons for, which may or may not happen to involve our or someone else’s happiness.
Obviously you can choose to focus only on goals that don’t involve happiness in any way at all, and maybe doing so makes some of the issues clearer. But I don’t think “involving happiness” / “not involving happiness” is the most fundamental criterion here; the distinction is actually, as your original terminology makes clear, between different modes of thinking.