There are two prominent depictions of marriage that Dickens draws in Oliver Twist The first is that marriage is necessary between young people who act so as to bring a baby into the world. This is clearly and forcefully shown in Chapter 1 in which Oliver's mother Agnes Flemming dies a tragic death at the hour of his birth and in which Oliver is swaddled in old worn out parish blankets that will mark and stamp him and dictate his life--for his whole life if a rescuer hadn't come along.
The second prominent way that Dickens depicts marriage is that it is generally (barring mitigating circumstances) commensurate with (i.e., corresponding to) the presence of goodness or badness in the people in the marriage. For instance, Mr. Bumble and Mrs. Coney are commensurately not good and they have a marriage in which each gets their just desserts--trouble. On the other hand Rose and Harry are commensurately good and have a marriage that brings them the joy of goodness. This brings up the point of mitigating circumstances in that Rose had a bit of a stain on her past, which however did not mar her innate character of goodness.
Charles Dickens must belive that marriage is based on love and not social status.