When Spinoza writes about God, it is not in the anthropomorphic sense of a God as usually portrayed by the Christian-Judaeo or Muslim varieties of religious scripture, i.e., very much like a person with human-like traits,  an authoritarian or father figure perhaps.  Someone who seems to take an active and personal interest in what the creatures he created here on earth are up to.

(And, it should be noted, demonstrating a personality  featuring some of the more regrettable human traits I can think of, such as being  narrow minded, vain, jealous, as well as being vindictive and vengeful! Anyone familiar with the Old Testament will know exactly what I am referring to!)

Does this mean that Spinoza was an atheist?  Not really, since he holds that God is the one and only unique and indivisible substance that the universe is made of. There are no other substances. The view is a bit more complex than that, and involves perceiving this substance through a variety of distinct attributes – such as Thought and Extension – but not its basic premise.

It is interesting to note that Albert Einstein – also once accused of being an atheist – followed Spinoza in rejecting the  anthropological concept of God,  saying,  instead,  that he believed in “… Spinoza’s God, who reveals himself in the lawful harmony of the world”.

So the point would be that, if God is everything, and everything is God,  this will render the concept of a distinct metaphysical entity over and above the world – the great creator –  logically and semantically empty (i.e., meaningless) since it doesn’t signify anything over and above the totality of the cosmos, and the name “God” ends up being just another label for it.