What is the meaning of the hadith that angels descend to listen to Surat Al-Baqarah, knowing that humans cannot see angels except in human form?

Humans are not capable of seeing angels in their original form. Allah Almighty says: (And if We had made him an angel, We would have made him a man, and We would have confused them as they are confused.) So, angels appear in human form when they interact with humans, as happened with Jibreel (peace be upon him) when he appeared to Maryam and in the stories of Ibrahim and Lut.

The hadith of Usayd ibn Hudayr and his listening to the angels when he recited the Quran indicates the possibility for some humans to see angels, but not necessarily in their original form, rather in a form that can be seen, just as Jibreel used to come to the Prophet (peace and blessings be upon him) in the form of Dihyah al-Kalbi.