It must be very difficult to avoid making a total mess of trying to update books which are of their era, like Agatha Christie's, so why on earth do they bother? As Margs says, the stories stand on their own. I remember listening to a radio adaptation of "Smallbone Deceased" by Michael Gilbert, which is one of my all-time favourite books and published in 1950. For some reason they tried to set it some decades later, and it just didn't work.
On a similar subject, we went to see "Scrooge" at the Pitlochry Festival Theatre, and as it's a musical, of course it isn't 100% true to the book, but that is fair enough for a musical,and it was very well done. However, spoiler alert, the Ghost of Christmas Past turned out at the last minute to be the ghost of Scrooge's dead sister. It added nothing to the plot - quite the reverse - and seemed to me to be an annoying irrelevance. Think I managed to keep my mutterings silent for the sake of the rest of the audience!