In a gnostic tradition such as Advaita, it is easy to conclude that Ishwara is unimportant. This, however, is not what the Upanishads reveal. They teach that Brahman is both saguna and nirguna. In Advatic teaching, nirguna Brahman is described as 'higher' than saguna Brahman (Ishwara) because nirguna Brahman is beyond comprehension.
This said, there is something else to consider. Just as no wave can create another wave, much less the sea from which it arises, all human beings are created, sustained and dissolved by Ishwara. It is for this very reason that we see even jivamuktas expressing devotion and worshiping the Lord who gives life to all.
Just as the vyavaharika and paramarthika levels are not-two, so, upon final analysis, we find that Brahman is One-without-a-second.
om tat sat