'“In vain have I struggled. It will not do. My feelings will not be repressed. You must allow me to tell you how ardently I admire and love you.”
Elizabeth’s astonishment was beyond expression. She stared, coloured, doubted, and was silent. This he considered sufficient encouragement, and the avowal of all that he felt and had long felt for her immediately followed. He spoke well; but there were feelings besides those of the heart to be detailed, and he was not more eloquent on the subject of tenderness than of pride. His sense of her inferiority, of its being a degradation, of the family obstacles which judgment had always opposed to inclination, were dwelt on with a warmth which seemed due to the consequence he was wounding, but was very unlikely to recommend his suit.'

That's the most we get of his confession. I would note - her inferiority in this respect is the station of her birth - not of her as a person or her mind. Class structures in Britain dictated everything back then. We don't know what he lists as her positive qualities, because we know nothing of the actual speech he gave her, just that her station and family are an obstacle that he feels he's valiantly overcome.

Then again, maybe you have a deeper understanding of what the stuck-up noblemen of the early 1800s would have detailed in a love declaration, more than someone like Austin who grew up during that time period.