The nonidentity problem does not establish that any livable future is acceptable. It pressures accounts that explain every wrong solely by comparative harm to an identifiable person. Duties of justice, thresholds for decent lives, or impersonal values may offer alternatives, though each requires an account of what present people must provide.
Compare two fictional towns that hand future residents different infrastructure. One maintains clean water and reliable transport; the other consumes its assets for present convenience. Assume different people will inhabit the towns under each plan. You can still ask what standards an inheritance should meet, even if no resident has a better alternative life. A useful answer specifies the conditions owed and how much current people may reasonably be asked to provide.