We don’t consider the material world to be perfectible because we aim higher. Bringing the “world”, primarily this word refers to each individual Jew (Olam Katan, a small universe) maximally refining himself, primarily through Torah and Mitzvot (which, admittedly, are not in themselves simple-to-define nor straightforward concepts), but it also includes creating a just society based on kindness (Chesed), fairness (Gevurah) and responsibility (Tiferet), to it’s highest state, often referred to (even when this term is not quite understood in its full implications) as Tikkun Olam, is not our final goal.
Rather, our goal is to create the conditions, following the “blueprint” (i.e. Torah) we’ve been given, that enable a discontinuous higher level of existence and consciousness, Olam HaAtid, The Future World, to emerge. Spending energy trying to “fix” elements of this world that either aren’t broken or whose “repair” isn’t necessary to our real goal, is, at best, a waste and a distraction/detour from our real goal.
Olam Hazeh, This World, is expected to be flawed and contains within its embedded structure, once again Torah, responses and reliefs (Karbanot, sacrifices, for example) to rebalance itself. We don’t know the “critical mass” of Tikkun required to launch the “quantum jump” to the higher reality, but we do know which actions of ours (i.e. Mitzvot) will help us achieve it.
The unperfectibility of this world, then, isn’t a cause for despair. Rather it’s a signal to rejoice that the true universe, Olam Gadol, is boundless beyond our imaginations.