You are not wrong of course, but on the scale between "between blindness towards biases, and ignoring human nature" your views fall 80%-90% towards "ignoring human nature".

Just to give you a more complete image, here's a thought:

People are not consequentialists, and they don't know clearly what they want.

In fact, there is nothing "absolute" that tells us what we "should" want.

And the happier you make people, the happier they tend to be with the goals you give them to work on.

If you also teach people rationality, you will get more scrutiny of your goals, but you will never get 100% scrutiny. As a human, you are never allowed to fully know what your goals are.

Looking at the "human nature" side, people who "care deeply" about EA-style things are just people who were in the right situation to "unpack" their motivations in a direction that is more self-consistent than average, not people who fundamentally had different motivations.

So my "human nature" side of this argument says: you can attract people who are in it "just for feeling good", give them opportunity to grow and unpack their inner motivations, and you'll end up with people who "care deeply" about your cause.