Some of the items (glazed ham in champagne sauce, lamb braised in red wine, grilled salmon in butter sauce, roast duck) sounds good and modern. Others (turtle soup, grouse with chaud-froid sauce) not so much. Most of the menus are written in French because that was the language of the courts of Europe.
Turtle soup is very good and still served in my native Louisiana. It is just hard to make because it requires French cooking skills and some rather exotic ingredients so you don’t see it much except at the fanciest restaurants.
It’s an aspic glaze poured over chilled, cooked foods. The name comes from taking a hot item and serving it cold. Like a lot of French traditions, it started as a parsimonious way of using up leftovers and morphed into an ostentatious display of technique.