If that's true. Why haven't we evolved into a species that doesn't harm each other or the environment?

Traditionally, harming other people and the environment has made it easier to feed your own children (or at least the children of your tribe) and have more of them.

Because that isn't what evolution does. Evolution is the process whereby traits that make reproduction more likely under selective pressures become more common. There is nothing in that process that necessarily implies a lack of harm to each other or the environment.

Evolution does not necessarily mean getting smarter or better in any way other than more adapted to the environment (natural and artificial). We could be getting stupider and more violent if that leads to hoarding more food and reproducing more in the given context. It's also not evenly spread throughout the species, some could be evolving various abilities while the rest are stuck in a plateau or even regressing.

Similarly with social progress. There is a common myth of linear progress through history, where humanity now is better than we were a century ago, a millenium ago, and ten thousand years ago. In some ways we're better, in other ways we don't even know what we've forgotten and lost.

What we want is conscious evolution, where we shape the direction that we wish to evolve towards. Unfortunately with the state of politics we've lost decades of progress in a very short time.

Because we became an incredibly successful species doing just that.

I think that that might be an aspect of the reproductive fitness of the 'hive' (or meta-organism) of all humans, rather than the genes in any individual or population.

I agree individual humans mostly seem to behave more like single-celled micro-organisms and it's a stretch to call it a collective-organism, but it's also not impossible to see the relevant analogous aspects though I think! (like, the internet could be one example?)

It's an interesting question whether the human species (or life-as-a-whole?) viewed as a single-system will be able to reproduce itself. Sounds like the question only makes sense when talking about settling elsewhere than Earth.. Mmm, reminds me of the Fermi Paradox. Will we make it through this!?!

Wars did become less violent, but the on scales of several hundreds of years. I'm not talking about industrializing death, but about desire of violence (civilian suffering, genocide). Evolution is very slow.