Does a sparsity of dialogue make Oliver a weak character?

A common criticism of Oliver Twist is that Dickens creates a weak character in Oliver because Oliver does not have extensive dialogue. Most often the narrator describes what Oliver is experiencing rather than lets him act it and talk it out. This device Dickens uses to build plot through narratorial intervention in the behavior and speech of the protagonist is a device that he used in his debut work, The Pickwick Papers. While Mr. Pickwick does have more dialogue than Oliver--bearing in mind that Pickwick is a person who puts himself forward while Oliver is a person who shrinks back away from contact--the narrator in Pickwick Papers has a similar role to the Twist narrator that features the same near proximity, the same pleasant intrusion with ironically satirical commentary, the same intervention between the character's deportment and the reader.
Such was the individual on whom Mr. Pickwick gazed through his spectacles (which he had fortunately recovered), and to whom he proceeded, when his friends had exhausted themselves, to return in chosen terms his warmest thanks for his recent assistance. (The Pickwick Papers)
Is Oliver rendered a weak, unbelievable, unsympathetic character because of Dickens' use of the device of narratorial intervention in character behavior and speech, which curtails dialogue? It is clear that in the early parts of the novel, Oliver is not deprived of his full-bodied strength as a sympathetic character. Even though the narrator tells us what becomes of Oliver day by day, we believe in Oliver; we know and feel deeply for him, for example, such as when he has bleeding feet after walking seven days with nothing but scarce and meager hand-outs:
[T]he light only served to show the boy his own lonesomeness and desolation, as he sat, with bleeding feet and covered with dust, upon a door-step.
It is true that we feel a weakening of the novel in the latter part, however, it is not clear that the fault lies in a weakened character development of Oliver. Plot devices that must be taken into consideration are the change in tone and mood that occur: We are struck by the strong presence of melodramatic characters surrounding Oliver [mood] and by the reduction in ironic satire contributed by the narrator [tone]. Perhaps these changes occur because Dickens' feels too deeply about the complications, falling actions and resolutions, or perhaps Dickens has a less clear vision of the story once the trouble and climax are passed.
Melodramatic characters do distract from the strength of the second half of the novel, though in all fairness, Dickens' Victorian period readers found it far less objectionable than modern readers do: Having come from the Romantic period in literature, Victorians had a taste for the melodramatically emotional. When thinking of melodramatic characters, we might think of the old woman on Oliver's journey to London who tearfully gave him "what little she could afford—and more." We might think of Nancy on her knees before Rose while begging her to keep her distance from such a corrupted one as she. We might think of Oliver being set upon in the lane on a lovely day by Giles in his "white nightcap" while beseeching the boy for news of Rose's illness.
Melodramatic characters surround Oliver far and near while he suffers his own melodramatic trials and joys. Yet this melodrama not cause us to care less about Oliver whose life we still closely follow and hope the best for as we do when he and Giles happen to see Mr. Brownlow alight from a carriage in the Strand:
'[He was] [g]etting out of a coach,' replied Oliver, shedding tears of delight, 'and going into a house. I didn't speak to him—I couldn't speak to him, for he didn't see me, and I trembled so, that I was not able to go up to him.'
My response to this common criticism is that Dickens' device of narratorial intervention, which deprives Oliver of voice, dialogue and direct action, does not render him an unrealistic nor a weak character. There are problems of language and melodrama that affect the character development of Oliver, but the problems are unrelated to the sparsity of Oliver's dialogue.