One option is to change our cities to be less hostile to the creatures that used to live there.
I made what you were stating clearer. Why would not saving endangered species lead to all the weakest lifeforms on the planet going extinct? Is it the fate of all of those lifeforms to go extinct without human intervention?
Specifically, just to hit this point home, the impact of humans is an extinction event comparable to the Cambrian–Ordovician extinction event, or the impact that killed off the dinosaurs. Who(or what)ever exists billions of years from now will be able to view the immensity of our impact assuming they still have the tools we have today.
It’s only a matter of time before we kill off what remains and you have to wonder, if we made earth so inhospitable to life, for how long can we survive ourselves?
That's a much better formulation.
It doesn't have to be "obvious that killing all the weakest lifeforms on this planet would cause bad things to happen" not to do it.
It just has to be possible and uncertain.
If you saw a fire spreading and was threatening someone's house, would you call the fire department, or otherwise attempt to stop it? Why or why not? Do you back up the data on your computer? Do you wonder why anyone takes pictures in order to preserve a moment in time, and would be upset if all their family photos got destroyed?
I don't think so, because many of the endangered animals are representative of entire ecosystems. Consider orang-utans and the forests they inhabit (many of which are being destroyed to collect palm-oil). If the animals have gone, it is even harder to make people want to preserve their environments in the face of relentless commercial pressure. Some endangered animals also help shape the ecosystems, e.g. when they are apex predators.
Once the animals are gone, recreating their communities is significantly harder. As stated elsewhere, most animals are better raised by their own species rather than humans outside the cage. For primates (e.g. woolly monkeys) individuals that have been raised in isolation in captivity also don't make good parents when they do eventually breed, sometimes abandoning viable young.
the real issue tho is that those species are part of a larger ecosystem, we're currently having large issue in Europe for having eradicated most boars' natural predators.
I'm not saying extinction is a good thing, but contextually it sounds weird to talk about us suffering from large issues from eradicating those predators.
The thing is that an ecosystem is a complex biological machine. When we go pulling out tiny sprockets from the machine, things break in ways we can’t predict and often don’t expect.
I am far less concerned about an asteroid hitting Earth and ending life as we know it, than I am about farmers eradicating insect “pests” leading to the collapse of life as we know it.
Which doesn’t explain why people are acting surprised that genetically modifying crops to produce insecticides will kill insects.