While I personally haven't experienced this in my marriage, my husband did in his previous marriage. And he was the culprit. There were times that he just didn't care. He was selfish. What do you do in those situations?
I think to say that every marriage goes through this is not exactly accurate, but it's certainly not uncommon. Especially if you've been having trouble for a while or you feel as though you are married to the wrong person. There are a million little reasons why marriages could end up this way. Lots of fighting, infidelity is rearing its ugly head, tons of reasons. If you are the partner struggling with feeling like your significant other just doesn't care anymore, it can feel defeating and hopeless. What is that saying, you can lead a horse to water but you can't make him drink? You can't make a person do anything they aren't ready to do. And it's probably not the case that the other person just doesn't care, maybe they also feel like too much has happened to come back from, or maybe they've been hurt too many times and are afraid that one more big blowout will be the straw that breaks the camel's back.
Breaking the cycle of hurt is difficult but not impossible. A lot of times, when couples get to this point, they tend to alienate themselves from other people because they are ashamed and embarrassed at what their marriage has become. If you have done this, get back into a group of people you love and trust and ask for help. Bringing in a third party, like a pastor, can do wonders because it allows people to talk about their problems while having a professional "mediate" which creates a new flow of communication. Get involved in a church together. Serve together somewhere. Change your habits of focusing on your marriage and focus on something else as a team. But mostly, ask for help and seek out professional counseling from either a minister or trained counselor. Do it now rather than later.