You’re not reading it so that the characters can be role models. Sherlock Holmes can be an unlikeable character and still have a bunch of awesome books written about him.
I happen to love Murder on the Orient Express. To the best of my recollection it’s very clean (though there are two very minor romances).
Funnily enough, I’m actually being a detective for Purim. You know, a big pipe, a magnifying glass, etc…
If you want to avoid all romance then you’ll find very few books. There are some really clean (and really good) Agatha Christie books but there’s always a teeny bit.