> At some point, a new habitat will reach a new balance with our introduced species and there's no going back.

> And yes, there may be less diversity in species all over the world (for the time being) thanks to that. But once the new species learn to reproduce and survive in a new place, then that is the "new" state of the habitat.

Yeah but won't that be just as true of a re-introduced de-extincted species? Mammoths / mammoth-ish elephants might change the new equilibrium in Siberia just like it changed when they were extincted in the first place... maybe the change could even be for the good. Why is the latter just accepted but the former is not?

There's this weird status quo bias that seems to say "ecosystems re-adjusting if humans deliberately re-introduce a species is artificial and must be bad" while also saying "ecosystems re-adjusting when humans literally do everything else that humans do is somehow natural or fated"

Human societies are coming to value and protect biodiversity. Extending your argument this is just another change in the habitat, one for which native species may be better adapted. Judging by the rules on what you're allowed to bring in to the country, Australia now appears to take invasive species very seriously.

I can imagine de-extinction and other genetic engineering techniques being useful to increase the amount of diversity in many habitats, which will theoretically give them a better chance of weathering huge environmental changes (as natural selection has a broader base of genes to work against). Since we need the biosphere to continue existing in a pretty narrow range of configurations in order to keep us alive (for example, we probably don't have the technology yet to sustain our civilization in the face of the whole planet becoming a desert, or not providing enough oxygen to breathe without artificial assistance), this might be a useful technique.