Let’s get this out of the way first: Albert Brooks basically makes this episode. We’ll see marital discord between Homer and Marge again and again (and again and again! and again! from different angles!), but it’s done so well here, and Jacques is so sleazy, that you have to love this first trip down infidelity lane. Who wouldn’t want to fall for Brooks’ Jacques?
Though one might nominally think this episode is about Marge, and her needs, I think a strong argument could be made that Homer is really the key figure here. His thoughtless birthday gift caps off a long history of being indifferent to Marge’s needs, and Patty and Selma rightly tease him for it. We don’t, however, see him learning anything from this experience — in fact, it’s never evident that he even understands what the problem is. (Bart: “When something’s bothering you, and you’re too damn stupid to know what to do, just keep your fool mouth shut.”) It isn’t surprising he makes no changes to his behavior, acknowledges his role in pushing Marge away, or apologize for his lack of interest in Marge, her hobbies, or her needs; the guy Doesn’t Get It, but Marge comes back to him anyway. (This becomes something of a recurrent theme in the show, where we are continually amazed that Marge’s love for Homer brings her back over and over again.)