The institution of monogamous marriage appears to be a corruption of the older, more reproductively productive institution of polygyny by successful males.
This type of polygyny wasn't nearly as widespread as you seem to think. In any case monogamous marriage has been around long enough that we can see that it works. The same isn't at all clear for what modern marriage is turning into.
I'm talking prehistoric here; we have evidence to suggest that raiding for females was a regular feature of human culture for most of our species' existence (discussed in this book.)
In any case, the modern, marry-for-love tradition, as opposed to marriage for political or economic expediency, is recent enough as to be practically untested in historical terms. It would be disingenuous to pretend that reverting to the institution of eighty years ago is in any way a return to a time-tested standard.
So you're playing the credence game, and you’re getting a pretty good sense of which level of confidence to assign to your beliefs. Later, when you’re discussing politics, you wonder how you can calibrate your political beliefs as well (beliefs of the form "policy X will result in outcome Y"). Here there's no easy way to assess whether a belief is true or false, in contrast to the trivia questions in the credence game. Moreover, it’s very easy to become mindkilled by politics. What do you do?
In the credence game, you get direct feedback that allows you to learn about your internal proxies for credence, i.e., emotional and heuristic cues about how much to trust yourself. With political beliefs, however, there is no such feedback. One workaround would be to assign high confidence only to beliefs for which you have read n academic papers on the subject. For example, only assign 90% confidence if you've read ten academic papers.
To account for mindkilling, use a second criterion: assign high confidence only to beliefs for which you are ideologically Turing-capable (i.e., able to pass an ideological Turing test). As a proxy for an actual ideological Turing test, you should be able to accurately restate your opponent’s position, or be able to state the strongest counterargument to your position.
In sum, to calibrate your political beliefs, only assign high confidence to beliefs which satisfy extremely demanding epistemic standards.