“The defense is that they did NOT, in fact, get a prophet like Moshe.”
Had they more than 7 mitzvos to follow in life, perhaps they, too, would have been worthy of a prophet like Moshe. Lifum Tzeara agra. But those nations were not willing to accept the achrayus and hishtadlus of following an entire Torah in their lives, and therefore were not worthy to the exact zechuyos of nevuah that am Yisrael was.