I mean people used to perform some practises based on scriptures but later they were opposed by people and scriptures and thus the practises changed or completely banished? Do we have to take the scriptures very seriously or can we suggest to edit/change them?
Scriptures do mention contradictory things. At least apparently they are contradictory. Scriptures themselves also mention that various contradictions can be found in scriptures.
See the following verses from Devi Bhagavatam:
Nârada said :-- “O Muni! The S’âstras are not one, they are many and they lay down different rules and contradictory opinions, How then Dharma is to be followed? And according what Dharma S’âstra?” Nârâyana said :-- S’ruti and Smriti are the two eyes of God; the Purânam is His Heart. Whatever is stated in S’ruti, the Smriti and the Purânams is Dharma; whatever else is written in other S’âstras is not Dharma. Where you will find differences between S’ruti, Smriti and Purânas, accept the words of the S’rutis as final proofs. Wherever Smriti disagrees with the Purânas, know the Smritis more authoritative. And where differences will crop up in the S’rutis themselves, know that Dharma, too, is of two kinds. And where the differences will crop up in the Smritis themselves, consider, then, that different things are aimed at.
Chapter 1; Book 11
We can not change or edit scripture just because few appear to give conflicting views. When such confusion arises how to reconcile is briefly mentioned in the above rules. For example, if Veda appear to go against itself then we have to understand that both the views are correct and Dharma in that case is of two kinds.