What has always bothered me about David Copperfield is that it is too idealistic.  Dickens presents a picture of David marrying a girl who is really all wrong for him, but then David is released from the situation when she dies in childbirth.  Dora is immortalized as the perfect young beauty.  It always seemed to me that Dickens just dispatched the wrong girl so that David could rectify his mistake and marry the girl he should have married in the first place, Agnes.  

In Victorian times, divorce was not an option.  It would have been scandalous.  David marries the silly, pretty Dora Spenlow because he is infatuated with her.  It is not a deep love.  He has more of a connection with Agnes.  Yet Agnes is not the stunning beauty that Dora is, so he doesn’t see it.  He marries Dora.  Then when Dora dies, he goes and marries the more comfortable Agnes.  

David did love Dora, in his own way.  He says she captured him. 

I heard a voice say, 'Mr. Copperfield, my daughter Dora, and my daughter Dora's confidential friend!' It was, no doubt, Mr. Spenlow's voice, but I didn't know it, and I didn't care whose it was. All was over in a moment. I had fulfilled my destiny. I was a captive and a slave. I loved Dora Spenlow to distraction! (Ch. 26) 

However, she frustrated him too.  She could not keep house, and she was very weak.  This is why Dickens has her die in childbirth, as David’s own mother did.  This is somewhat poetic, even though it is sad.  David came full circle, marrying his mother.  Freud would have something to say about that. 

When Dora dies, David moves on to Agnes Wickfield.  Agnes is everything Dora is not.  She is intelligent, compassionate, and motherly.  She is the perfect girl for the needy David.  Yet she seems like his second choice, because he had already married Dora. 

I was never unmindful of Agnes, and she never left that sanctuary in my thoughts ... I loved her none the less; I thought of her as the same benignant, gentle angel in my life… (Ch. 28) 

If David had married Agnes to begin with, it would have been a marriage of comfort and friendship as well as love.  The entire situation with Dora is unrealistic.  I think that this different ending would make the book less dramatic, but more satisfying.