Monogamy- is it unrealistic?

Catherine Deveny writes that “A bit on the side is perfectly understandable” and adds:

Lifelong monogamy is an unrealistic expectation that makes people feel like
failures. And if you don't believe me, take one look at the divorce statistics.
People are torn between their emotions and an archaic expectation that was
conceived when the average life expectancy was 30. Monogamy is a wonderful way
to maintain what the church and the state would call "social order" and, more
importantly, to ensure paternity to hand wealth down to offspring.

I hold the view that monogamy is still realistic and practical.

Granted that we are at times attracted physically to others, but when it comes to companionship we seek the warmth of marriage. In fact I hold the view that marriages fail, not because of physical incompatibility but more because of lack of warmth and companionship.

Do you agree?