The case for one God does not rest on the claim that many agents can never cooperate. It rests on what is meant by the Creator: the independent, unlimited source of all existence, not a group of powerful beings sharing a project.
The strongest form of the question
A polytheist can reasonably say that cooperation is common. A large building may have many architects, and a complex universe might, in principle, result from several divine agents dividing responsibility. The Quran's appeal to rivalry, therefore, does not by itself prove that multiple gods must fight. Cooperation is logically possible among limited beings.
That objection is fair as far as it goes. It shows that the mere complexity of the universe is not a proof of one Creator. Nor does the verse mean that every imagined group of supernatural beings must behave like quarrelling humans.
What "Creator" means
The decisive question is whether these beings are truly ultimate and independent. If each has complete power over all reality, then their wills must either be capable of conflict or be necessarily identical.
If they can will opposite things, both outcomes cannot occur in the same respect. If one will prevails, the other is not omnipotent. If neither prevails, neither is omnipotent. If their wills always agree, that agreement requires an explanation. Is it imposed by a law above them? Then that law, rather than they, is ultimate. Is it part of their own nature? Then their distinction is not a division of independent sovereignty, but merely a distinction without any explanatory work.
There is also a deeper point. If two supposed gods differ, something must account for the difference. One may possess a power the other lacks, or one may be restricted in a way the other is not. Such limitation makes each dependent and therefore not the absolute source of everything. If they do not differ in any reality relevant to divine action, speaking of two ultimate gods adds nothing.
How the Quran's argument fits
"Had there been in the heavens and the earth gods besides Allah, both would have been ruined. So glorified is Allah, Lord of the Throne, above what they describe."
Quran 21:22
The verse is not merely predicting bad teamwork. It points to the incoherence of multiple independent sovereigns governing one total reality. The next passage makes the issue clearer:
"Allah has never taken a son, nor has there ever been with Him any deity. Otherwise, each deity would have taken what it created, and some would have tried to overcome others. Glory be to Allah above what they describe."
Quran 23:91
Classical scholars understood this as an argument from divine sovereignty and the unity of the ordered universe. Multiple lesser powers may cooperate, but then they are not creators in the absolute sense. They are created, dependent agents.
This establishes that tawhid is the best rational account of an ultimate Creator; it does not prove, from complexity alone, every detail of Islamic theology. The Quran's further claims about Allah's names, attributes, and worship come through revelation. But once "God" means the necessary and independent source of all things, plurality is not an added explanation - it is an unnecessary and unstable one.