The example of those who disbelieve is like that of one who shouts at what hears nothing but calls and cries [i.e., cattle or sheep] - deaf, dumb and blind, so they do not understand.
Allah states that if the disbelievers and polytheists are called to follow what Allah has revealed to His Messenger and abandon the practices of misguidance and ignorance that they indulge in, they will say, "Rather. We shall follow what we found our fathers following," meaning, worshipping the idols and the false deities. Allah criticized their reasoning:
أَوَلَوْ كَانَ ءَابَاؤُهُمْ
((Would they do that!) even though their fathers), meaning, those whom they follow and whose practices they imitate, and:
لاَ يَعْقِلُونَ شَيْئًا وَلاَ يَهْتَدُونَ
(...did not understand anything nor were they guided) meaning, they had no sound understanding or guidance. Ibn Ishaq reported that Ibn `Abbas said that this was revealed about a group of Jews whom Allah's Messenger ﷺ called to Islam, but they refused, saying, "Rather, we shall follow what we found our forefathers following." So Allah revealed this Ayah (2:170) above."
When these mushrik people were asked to follow the injunctions revealed by Allah through His Messenger, they refused to do so and insisted that they would rather follow the customary practice they had inherited from their fathers because, as they assumed, their models were divinely appointed to follow the way they adopted. Allah Almighty refutes this position of theirs by asking how could they go on following the ways of their fathers, under all conditions, to the exclusion of all other ways, even if their fathers did not understand much about the true faith, nor were they blessed with guidance given by their Lord?
Once an object, which is not God, is accepted as God as a result of man’s superstitious attitude, many other accompanying evils ensue. An animal may come to be regarded as possessing supernatural powers—something possessed only by God. That animal is then held to be a means of achieving proximity to God and is expected to be a source of blessings. In the next generation all these superstitious beliefs become firmly rooted in the human psyche and are upheld with great zeal and fervour as the sacred way of the forefathers. At this stage, people become resistant to any rational analysis of these superstitious beliefs. The situation deteriorates further with succeeding generations. People reach a level where they are totally unable to hear or understand any argument put forward to them. They act as if they have neither eyes nor ears to see and hear, nor brains to give thought to any argument presented to them.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.