Buddhism is about enlightened self interest - to sharpen one's focus onto the important things - and not just the things that are efficient distractions for most people. So, self improvement or societal improvement is definitely not a problem with Buddhism.
If you woke me up at my deepest sleep, when I am the groggiest, I am of little use to anyone, until I wake up fully. Similarly, to be of use to anyone, whether ourselves or others in our lives, or the world at large, we must first be awakened to reality of life. Or we compound errors, like someone who's just woken up, and can't open his eyes too well.
Take the case of a professional, say a doctor. A junior doctor will likely lose sleep over a mishap, like the loss of a patient, she will agonize over what went wrong, what could have been done to save him, and so on. Whereas, a senior doctor would know nothing more could have been done, and goes about life after a moment's reflection. Nothing surprises the senior professional in her sphere of competence.
It may be a whole another story outside their sphere of competence - if the senior doctor lost a lot of money on the stock market, she may react like a child, crying over it, while the senior banker shuffles off home equanimously after a similar loss because this loss and gain happens to him every day.
Life happens to all of us everyday but we cry like little children at
life's agonies, and squeal at life's pleasures. We aren't very mature
An enlightened Buddhist looks at all life like a senior professional. With maturity. If something needs doing it is done, if something remains undone despite doing everything, there is no panic, it is just life.
We are in no hurry to arrive, we are in no reluctance to depart.
Buddhism isn't only about denial of the self. That would be an extreme view. Just like belief in a self is an extreme view. Initially when people are unenlightened they can't even conceptualize the idea of a world without a self. At the next stage of awakening, they come to terms with the world that is empty of the self. At the next stage they come to terms with the world where a self is and isn't. They have successfully let go of either extreme.
At this final stage they are neither obsessed about lack of self improvement, nor are they lazing about without self improvement. They have developed a capacity to accept things for what they are, and react suitably. This doesn't mean they let life happen to them like an immobile rock, nor are they supermen who dodge everything life throws at them.
They are in one word - very mature. Like a consummate master of life who has seen it all, stepping out of the way of problems that can be avoided, and accepting what cannot be avoided as necessary.