How can anyone say that the time before Gen 1:1 is irrelevant ?

Because they are gullible enough to believe that Genesis is something other than a myth.

Because the whole Bible is a book on salvation, the righteous can unlock its secrets. In the dominion of heaven Genesis 1 has the meaning of people without God being formless, empty and living in darkness even while the Spirit of God hovers over them. Only when they respond to Gods call and His precious gospel of the water and the Spirit, does He say, 'Let there be light." But first the waters must expose the dry land underneath. This means that sinners needs to expose themselves to the Light and acknowledge themselves wholly, with all their sin. And only then can God sow the good seeds of the true gospel in their hearts, to produce a harvest of righteous fruits.

How can God become irrelevant ....He was always there, even before Gen1:1

There was no time before Genesis 1:1. God is infinite. Therefore He has always existed without beginning or end.

Because there was no time before the universe was created.

because time, being a physical dimension didn't exist yet