NB: I reread and reviewed Jude the Obscure in 2018.
The flaw with Jude the Obscure is neither its theme nor its characters. The flaw is with the narrative, which, slowly-paced, is only lengthened by the vacillation of Hardy's characters.
At first, I empathized with young Jude Fawley. An intellectual at heart, even as a child, he dedicates himself to becoming an autodidact and strives to gain admittance to the university. His plans hit a snag when he allows himself to be seduced by the attractive Arabella, who tricks him into marriage by faking a pregnancy. Marital woe ensues, the couple separates, and Jude falls for his cousin, Sue Bridehead. Still, even when it seems like he has everything he wants, Jude fails to be happy, and tragedy dogs him at every step. I don't think it will spoil anything to mention that Jude's fate is the same as most of Hardy's main characters. That man just can't bear to give his stories a happy ending!
Much of Jude's misfortune originates from external stimuli, yet Jude often fails to stand up for his beliefs. This results in most of his marital strife (in both relationships) and his failure to realize his intellectual dream.
The theme of unfulfilled intellectual ardour particularly fascinates me. If I hadn't been born into a situation where I had the opportunity to get an education, get a job, go on to university, would I be like Jude? Despite his most earnest attempts to educate himself, Jude eventually becomes bitter about both universities and the church. Hardy seems to be creating a dichotomy out of society: you can be a happy intellectual or a happy working man, but a working man intellectual can never be satisfied. While I don't think that's as true today as it was in Victorian times, it still contains a nugget of wisdom: too much compromise, too much vacillation, means you can never be happy. This moral bears out in Hardy's other major motif, marriage.
Modern readers must remember that the norms around marriage in Victorian society differed from what we consider normal today. We seldom bat an eye at divorce anymore, whereas it was highly controversial in the Victorian era. Jude the Obscure met with considerable opposition, particularly from the clergy, some of whom publicly burnt copies of the novel.
However, the book itself isn't an attack on the institution of marriage (nor is it a particularly affectionate affirmation). Hardy instead shows us two examples of where a hasty marriage is a mistake and one example of where hesitation--and eventual failure--to marry proves the relationship's downfall. Jude hastily marries Arabella when she claims she's with child, yet it soon becomes clear that their inclinations are incompatible. When Jude succeeds in persuading Sue to live with him "as his wife" but fails in persuading her to marry him, he lays the ground for her eventual abandonment of him in favour of her first husband. Jude continually acts based on what he believes will make him happy; Sue attempts to act based on what she believes is her duty going as far as to impose harsh penance upon herself for perceived wrongs. Neither of them succeeds in achieving happiness or satisfaction.
I was kind of disappointed that Jude ended up with Arabella in the end, although I was not at all surprised. Nor was I surprised when Arabella tricked him into marrying her (again, this time plying him with alcohol instead of sex!) and then she regretted it afterward. Interestingly enough, it's fair to say that Jude and Sue both change over the course of the book, but Arabella does not. She remains transient, always searching for the next man, the next lifestyle. First she marries Jude, then she takes up with a man in Australia, whom she follows back to England and persuades into marriage. Once he dies, she remarries Jude after he separates from Sue. She seldom shows any concern for others beyond how their situation affects hers; even her sadness over her own child's suicide is ... a formality.
I can't help but wonder how much of Arabella's character is of her own choosing and how much was forced upon her by circumstance. At first, I felt some sympathy for her when she and Jude were courting. Jude gradually becomes disillusioned with his first love as she reveals that she is not quite as pure as he might like to think: her long hair is merely an extension, and she once worked as a barmaid in a pub! Indeed, Hardy never comes right out and says that she lied to Jude about being pregnant--her friend Annie, who originally suggested getting pregnant as a means of snaring Jude, plants this suspicion in our minds when she congratulates Arabella on being so cunning. Thus, it's possible to paint Arabella in a more sympathetic light if one chooses to believe she actually thought she was pregnant. I suspect she was just manipulating Jude, however. Her later actions prove she's not beyond manipulating men for her own designs.
The other major female character, Sue, differs greatly from Arabella. This is probably part of her attraction for Jude: her perceived chastity and devotion to the arts and education is an antithesis to Arabella's worldliness and pragmatism. In Sue, Jude looks for an escape from the oppressive realism of his first marriage and his day job as a stonemason. Yet Sue also manipulates Jude, confessing that she would have him love her even though she doesn't (at first) love him. Although this may seem like a rather derogatory portrayal of women at first glance, it's more social commentary than misogyny: Sue, living alone in the city, must get by with whatever advantages she has; her beauty is one of them.
On the level of social commentary, Jude the Obscure focuses a great deal on the notion of upward mobility. Women, of course, have the option of "marrying up" on the basis of their charm; Sue does this to an extent with Phillotson. Men, on the other hand, as exemplified by Jude, are typically stuck in their social position, particularly if they're of the working class. Hardy is very critical of the inflexibility of the English educational system. At the same time, if a man doesn't have a "proper" marriage, it can cost him his job--this happens to Phillotson after he allows Sue to leave him and "live in sin" with Jude. Both sexes are painfully aware of their limited options in terms of moving up in society; Phillotson and Arabella alike are given to "plotting" how they can further advance themselves.
Jude the Obscure is profound in the sense that most of Hardy's work is profound: it's a polemical novel in which the characters are part metaphor and part people. However, as a narrative it falls short of being entertaining. Both its length and its repetitive plot structure are daunting and undermine the book's true strength--its characters. As Hardy's last novel, it's worth examining Jude the Obscure in the context of his oeuvre. I would not recommend it to first-time Thomas Hardy readers though.