That is not what the Quran says though. You must have learned this idea from somewhere else. I think You should weigh your idea against the verses of the Quran.
The Quran calls itself a clear book many times and a clear recitation. Anyways, we've presented evidence from hadiths and Quran. I think you don't change views no matter what evidence is shown.
There is also to consider what Satan cast (sorcery):
وَمَا أَرْسَلْنَا مِنْ قَبْلِكَ مِنْ رَسُولٍ وَلَا نَبِيٍّ إِلَّا إِذَا تَمَنَّىٰ أَلْقَى الشَّيْطَانُ فِي أُمْنِيَّتِهِ فَيَنْسَخُ اللَّهُ مَا يُلْقِي الشَّيْطَانُ ثُمَّ يُحْكِمُ اللَّهُ آيَاتِهِ ۗ وَاللَّهُ عَلِيمٌ حَكِيمٌ | We did not send any apostle or prophet before you but that when he wished Satan cast/threw in his wish. Thereat Allah nullifies whatever Satan has cast/thrown, and
then Allah makes clear/firm His signs, and Allah is All-knowing, All-wise. | Al-Hajj : 52
لِيَجْعَلَ مَا يُلْقِي الشَّيْطَانُ فِتْنَةً لِلَّذِينَ فِي قُلُوبِهِمْ مَرَضٌ وَالْقَاسِيَةِ قُلُوبُهُمْ ۗ وَإِنَّ الظَّالِمِينَ لَفِي شِقَاقٍ بَعِيدٍ | That He may make what Satan has thrown in a test for those in whose hearts is a sickness and those whose hearts have hardened. Indeed the wrongdoers are steeped in extreme defiance. | Al-Hajj : 53
وَلِيَعْلَمَ الَّذِينَ أُوتُوا الْعِلْمَ أَنَّهُ الْحَقُّ مِنْ رَبِّكَ فَيُؤْمِنُوا بِهِ فَتُخْبِتَ لَهُ قُلُوبُهُمْ ۗ وَإِنَّ اللَّهَ لَهَادِ الَّذِينَ آمَنُوا إِلَىٰ صِرَاطٍ مُسْتَقِيمٍ | [And also for the reason] that those who have been
given knowledge may know that it is the truth from your Lord, and so they may have faith in it, and their hearts may be humbled before Him. Indeed Allah guides those who have faith to a straight path. | Al-Hajj : 54
And regarding hard hearts in the past regarding the revelations of Bani-Israel Prophets (a):
فَبِمَا نَقْضِهِمْ مِيثَاقَهُمْ لَعَنَّاهُمْ وَجَعَلْنَا قُلُوبَهُمْ قَاسِيَةً ۖ يُحَرِّفُونَ الْكَلِمَ عَنْ مَوَاضِعِهِ ۙ وَنَسُوا حَظًّا مِمَّا ذُكِّرُوا بِهِ ۚ وَلَا تَزَالُ تَطَّلِعُ عَلَىٰ خَائِنَةٍ مِنْهُمْ إِلَّا قَلِيلًا مِنْهُمْ ۖ فَاعْفُ عَنْهُمْ وَاصْفَحْ ۚ إِنَّ اللَّهَ يُحِبُّ الْمُحْسِنِينَ | Then, because of their breaking their covenant We cursed them and made their hearts hard:
they change/move words from their places, and have forgotten a part of what they were reminded. You will not cease to learn of some of their treachery, excepting a few of them. Yet excuse them and forbear. Indeed Allah loves the virtuous. | Al-Maaida : 13
And said:
وَحَسِبُوا أَلَّا تَكُونَ فِتْنَةٌ فَعَمُوا وَصَمُّوا ثُمَّ تَابَ اللَّهُ عَلَيْهِمْ ثُمَّ عَمُوا وَصَمُّوا كَثِيرٌ مِنْهُمْ ۚ وَاللَّهُ بَصِيرٌ بِمَا يَعْمَلُونَ | They supposed there would be no testing, so they became blind and deaf. Thereafter Allah turned to them (mercifully), yet [again] many of them became blind and deaf, and Allah watches what they do. | Al-Maaida : 71
Without nullifying what Satan cast, the signs won't be clarified and made clear. And this why a soft heart is needed that turns to God and also believes in the unseen as to see Satan and his magic and his forces so to defeat the dark magic and the opponents.
Also, the verse 3:7 says itself the clear signs are the mother/original book. It means that is the original intent by God and is the original Quran revealed to Mohammad (s).