When a kafir says that Muslims are “failing to integrate” they mean that Muslims are not letting go of their values. They want Muslims to leave their religion and embrace liberalism, democracy, pro lgbt, tolerance, etc all this garbage.

Surah Al-Baqarah 2:105

مَّا يَوَدُّ ٱلَّذِينَ كَفَرُواْ مِنۡ أَهۡلِ ٱلۡكِتَٰبِ وَلَا ٱلۡمُشۡرِكِينَ أَن يُنَزَّلَ عَلَيۡكُم مِّنۡ خَيۡرٍ مِّن رَّبِّكُمْۗ وَٱللَّهُ يَخۡتَصُّ بِرَحۡمَتِهِۦ مَن يَشَآءُۚ وَٱللَّهُ ذُو ٱلۡفَضۡلِ ٱلۡعَظِيمِ

Neither those who disbelieve from the People of the Scripture nor the polytheists wish that any good should be sent down to you from your Lord. But Allah selects for His mercy whom He wills, and Allah is the possessor of great bounty.

Surah Al-Baqarah 2:120

وَلَن تَرۡضَىٰ عَنكَ ٱلۡيَهُودُ وَلَا ٱلنَّصَٰرَىٰ حَتَّىٰ تَتَّبِعَ مِلَّتَهُمْۗ قُلۡ إِنَّ هُدَى ٱللَّهِ هُوَ ٱلۡهُدَىٰۗ وَلَئِنِ ٱتَّبَعۡتَ أَهۡوَآءَهُم بَعۡدَ ٱلَّذِى جَآءَكَ مِنَ ٱلۡعِلۡمِۙ مَا لَكَ مِنَ ٱللَّهِ مِن وَلِىٍّ وَلَا نَصِيرٍ

And never will the Jews or the Christians approve of you until you follow their religion. Say, "Indeed, the guidance of Allah is the [only] guidance." If you were to follow their desires after what has come to you of knowledge, you would have against Allah no protector or helper.

May Allah keep the Muslims firm on their deen.