Relation of the Fitrah to Islam
The greatest connection that the Fitrah has with Islam is monotheism (Tawheed). Hence our name 'Fitrah Tawheed'. Allah has created the Fitrah for us so that we can recognize and worship Him.
Thus, the concept of the Fitrah largely has to do with monotheism. In the Quran, Allah often pairs natural disposition with the religion of Ibrahim (Hanif). That is because the two put a lot of emphasis on monotheism.
So turn your face towards the religion Hanif. (Follow) The natural disposition with which Allah created mankind.
30:30 Quran
Thus there are no exceptions when it comes to the innate Fitrah. Every child is born with it, inclined to the pure worship of Allah. But the child is then changed by parents to a Christian, Jew or other religion.
Abu Huraira reported:
The Prophet (ﷺ) said: “Every child is born with the Fitrah. His parents then make him a Jew, or a Christian, or a fire worshiper. If an animal gives birth to a youngster with intact limbs, do you see any error?"
Then Abu Huraira recited the Quran verse: "The Fitrah with which Allah created mankind".
[Sahih Bukhari 1292 and Sahih Muslim 2658]
Abu Huraira reported:
The Prophet (ﷺ) said: “The mother of each person gives birth to him according to his Fitrah. It is then his parents who make him a Jew, Christian or fire worshiper. If his parents had been Muslim, he would have remained Muslim too.
[Sahih Muslim 2659a]
Because every child is born with the Fitrah, we recognize the Oneness of Allah. We recognize and acknowledge monotheism when we continue to follow the Fitrah.
Therefore, we can worship Allah as He wants to be worshiped. And that is without associating partners with Him. We observe the Tawheed (Oneness of Allah) and avoid Shirk (idolatry).
We are informed by the Fitrah what major shirk entails. For example, you do not need to be explained that worshiping others beside Allah is idolatry. This prevents us from being ignorant of major Shirk acts when we are aware of those.