Couldn’t agree more with everything you said. IMHO, selfishness is the #1 cause of divorce. Too many people go into marriage thinking nothing in their lives should/will change. Big mistake.
Yes, people who are unwilling to make personal sacrifices for the health of the union should not get married. It’s almost 100% guaranteed to fail if they do.
And you’re right about marrying more selfish people. Resentment will build (in the more selfless and least appreciated spouse) and things will spiral out of control at some point. I think this is where you see the divorces after 20 years of marriage and after all the kids have grown. Some people (both men and women) have so much resentment built up (from sacrificing everything while not being appreciated for it), that when they finally finish up with what they perceive to be their committment to their children, they blast out of their marriages as fast as they can. This is why open and honest communication **and empathy** throughout the marriage is so important.