I see no reason to value the current ecosystem. It’s completely arbitrary.

If we had tech capable of it, would we be obligated to restore past ecosystems? What if doing so destroyed the current ecosystem? At some point every species alive today displaced another.

What makes the ecosystem as it exists right now especially valuable?

In my view? Unlike ecosystems, animals are actually alive and can suffer. I choose to value their lives over an arbitrary relation of animals at a point in time called an ecosystem.