Oh, we've completely fucked ecosystem balance. That said, that doesn't mean human managed ecosystems are bad, or that actively managing ecosystems is bad. It's just a lot of work, and you have to figure out what you want that ecosystem to look like and what function it will have.
Arguably, self sustaining (e.g., natural) ecosystems are ideal soley because we don't have to manage them.
There is also value natural ecosystems because that's how they evolved, and everything fits nicely, but we've long since impacted all ecosystems to some degree so the point is kind of moot.