If you visit each other’s churches, you may be struck by the similarities, assuming that the liturgies are well-celebrated.
You might try to locate a copy of Catholic Matters, by Richard Neuhaus. Neuhaus is a former Lutheran (LC-MS) pastor who converted, and is now a Catholic priest. There is a chapter in the book where he gives his conversion story, and he is very gracious and appreciative about his Lutheran upbringing. In fact, I sent a copy of the book to my parents as the first gentle “hint” that I was thinking about converting. That chapter, in particular, might stimulate some hopefully respectful discussions about Lutherans and Catholics.