I think that it's sort of just something that psychiatrists invented so that they could profit from identifying problems, and alleviate people from the pressures of their own responsibilities as the influence of religion wanes in the world.
It's actually kind of a comforting thought to imagine that there is no such thing as self-esteem-- the tag 'low self-esteem' implies that a negative pattern of behaviors and attitudes is some abstract component of your identity, and thinking about it thusly sort of makes it harder to overcome.
So yeah, I'm of the opinion that it's a capitalist social abstraction… but then again, I don't know if I know so much about it.
When you make the willingness to learn the basis for your self esteem, that cuts through a lot of other issues as well. And it's one of the few forms of self esteem that actually keeps you open to change. For many of us, self esteem means thinking that basically we're good people — which means that we have to keep trying to look back on our past actions to see evidence of that. And then, of course, we run across things that don't support that idea, and so we block them out of our minds. We don't like to think about them. In many cases those are precisely the things we need to learn from.
From: Self Esteem by Thanissaro Bhikkhu