Just because you don't like the new album this does not mean that Depeche Mode have to change. They make the music they want to make. The people who like it should buy their album. The people who don't like it should not buy their album. It is that simple. Of course you can ask them if they are willing to change their music in order to please you ... but I assume that the answer will be 'no'.
Maybe the number of fans is decreasing but there are still some left. Check the album charts next week and you will notice that the party is not over yet.