You are confusing a subtype of monogamy with all possible variants of monogamy.

You’re describing patriarchichal, state/religiously sanctioned and ordained marriage.

I’m describing two people who are just having a relationship with each other, who discuss and agree to how that relationship works.

Doesn’t have to involve religion or even the state.

Just a commitment between two people, none over the other, both as close to equal as possible.

I’ve gone to significant lengths to explain how yes, monogamy is often formalized in a fucked up way… but it doesn’t have to be.