We know, there was a time, when Sun was worshiped by so many people.
And there was a time, when Moon was worshiped by so many people.
And there was a time, when many deities made of stones were worshiped and now their worship has been discarded.
And there was a time, many saints were worshiped and now no one knows those saints names.
As time moves on, people keep creating new deities and worship them and as time moves on, many of the previous deities are discarded and forgotten.
But God has been worshiped since the beginning and will be worshiped till the end.
It means, God is a true deity and there is no deity except God and there is no one worthy of worship except God.
And your god is one God. There is no deity [worthy of worship] except Him, the Entirely Merciful, the Especially Merciful.