After having checked the Wikipedia entry for the 8th Arrondissement, I was most interested in the Madeleine church,
- first, because it looks nothing like the other cathedrals,
- second, because it was the site of Chopin’s funeral service which was delayed by a political dispute involving whether women could sing in the choir (Mozart’s Requiem), and
- third, because one of the most affordable lunches in Paris is served here during weekday lunch hours. https://www.timeout.com/paris/en/restaurants/foyer-de-la-madeleine
And, yes, there are other things to do in the 8th, the busiest place in Paris, with 5-star hotels and business interests, plus the iconic Champs-Elysees and Arc de Triomphe and four or five small museums.