The most significant impact on English culture from King William the Conqueror replacing English nobles with nobles from Normandy was that French words became part of the English language.
After the Norman Conquest of 1066, the Norman culture heavily influenced English society, leading to the incorporation of a vast number of French words into the English language, especially in areas such as law, governance, art, literature, and cuisine. This linguistic shift marked the beginning of Middle English and significantly shaped English vocabulary and syntax.
While it is true that there were aspects of corruption and conflict, and the presence of French nobles did create tensions regarding property rights, the most direct and lasting cultural change was the infusion of French language and culture into England.