This comes from someone who's working on his third marriage:
Although the primary reason for marriage has not changed--love--the reasons for staying together has. Marriage requires work...daily work. A good marriage requires daily devotion to someone other than yourself. Most of us aren't willing to put in the work. Longevity requires someone you can work with, to accomplish your goals; like-mindedness in how you see your future; honesty and respect, in how you treat each other and how you carry yourself; open and honest communication...without secrets. These are necessary if you are to have your mate's back.
All too often, people marry without getting to know their mate. They're quick to say, "I know all I need to know." But, they don't. They know the sex is good; they know their mate is pleasing to their eye. However, beyond the name, the work location, and where they live, they don't know very much. What are their hobbies, their favorite foods, do they want children? More basic things: Am I willing to accept their faults? Can I live with their snoring...their arguments...their pettiness? You may think it's not important, but if you're mate's method of communication when angry...is to scream at you and treat you like a child...that grows old very fast. He/She will let you know this long before marriage, but you have to pay attention to the signs.
Also, many do not have an understanding of what marriage is...what it means. Yes, it means you're joined together...but to what end? Does it mean she's responsible for the housework...and he's responsible for the outside work? Does it mean everything is shared...the work and the pleasure? Does it mean his money is her money and vice-versa? Too many don't know their role: Who is the head of the house? You may claim that you're beyond that...but there can't be two CEOs in the same company. Someone has to be the final decision making authority. Yes, it's great when you can both contribute to the final decision...but if you cannot agree, what then? Is that a game changer?
As you might imagine, there is no simple answer to your question. The best advice I can give is to find someone you can laugh with...someone you can work with...someone you're in like with...someone you call a friend, preferably your best friend. If you find such a person, hold on to her/him even if you don't love her/him to begin with; eventually, you will. Once you find that person, make sure that person feels the same way about you. If so, you will grow to have each other's back...because that person will always put you first...and will never let anyone put you down.
Marry for the right reasons. The worst thing you can do is marry only because your mate is good in bed...and you don't want to see him/her with someone else. That doesn't mean you shouldn't marry someone who's good in bed; but that should not be the only reason.
As for today's generation, it's not that they face more challenges than their fore-parents, but today's generation are less needy...so they aren't compelled to stay with someone if they have to work at being happy. They have fallen into a concept of "convenience." Once it's no longer convenient, they feel it's time to go...where their fore-parents felt that that was the time to grow...together.
Marriage works when people are willing to put the work in to make it work.