Well, their descendants are pretty much everywhere you see something greenish, so it seems to have worked out.

> We build skyscrapers and Howitzers for intentional purposes, not because we excrete them.

We also emit pollution for intentional purposes. They might not be particularly noble purposes, but they're 100% intentional by each of humanity's individual parts.

I think you're confusing "the tools we use" versus "the ways we change the globe". Most of the worldwide changes we cause are not explicitly planned or built, but side-effects of the "metabolism" of our civilization.