What would the implications be if there was no such thing as anything immaterial in any way, shape or form?
The majority of materialists hold that anything immaterial is reducible to or dependent on the material. To hold that there is absolutely nothing immaterial at all is called eliminative materialism and is associated with Alex Rosenberg and Dan Dennett, among others.
Eliminative materialism starts with scientism, which says that only science can provide a complete description of matter and that the material is all of reality. Therefore, anything that is immaterial cannot possibly exist in any sense.
The following is a list of issues usually considered in discussions on materialism and how eliminative materialists handle them. Other types of materialists have a more moderate position on the same issues.
Thoughts: That thought you just had about your cat. Was it really about your cat? A material thing cannot be “about” another material thing. You wouldn’t say that a rock is “about” another rock, would you? Therefore your thought was about nothing at all and all your thoughts are meaningless.
Truth, knowledge, justice: These are just illusions in your mind that have no scientific basis, along with all other ideas and concepts.
Words: How about the word “cat”? Is it about actual cats? Words are supposed to be linked to their definitions, but what is this link? It is impossible for a physical thing to be linked to another one in this way. Therefore the word “cat” has nothing to do with cats and all words are meaningless.
Consciousness: An illusion.
Beliefs, desires, purposes: More illusions.
Your “self”: Science doesn’t know about “selves”. This is another illusion.
Morality: Right and wrong have no basis in science and therefore do not exist in any sense.There are no exceptions, not even murder. To say that anything is wrong is just meaningless word salad. 
Mathematics: I was unable to find out if eliminative materialists have a position on mathematics, but given their positions on thoughts and words, I’d imagine they would reject mathematics as being meaningless symbols.
You get the idea. Other things the eliminative materialist denies include meaning, free will, God, the soul and life after death.
The majority of materialists are not eliminative materialists. Nevertheless, the list above shows what topics the materialist must ultimately deal with and explain. It is clear that there is far more to it than simply saying “no God, therefore materialism”.
 To be fair, I don’t know if anyone apart from Alex Rosenberg has actually said this. He says that nihilism is true and we should be “nice nihilists”.
Eliminative materialists have written books, including:
- “The Atheist’s Guide To Reality”, by Alex Rosenberg
- “Consciousness Explained”, by Daniel Dennett
For a critical look at eliminative materialism from a non-materialist philosopher, go to https://www.firstthings.com/article/2011/11/scientia-ad-absurdum