Catholics aren’t Sola Scriptura Christians. Sacred Scripture is important but there is also Sacred Tradition and the Magisterium to ‘bind and loose’. I hope I got this right.
Polygamy didn’t appear until after the Fall.
The original design of marriage was one man and one woman. Adam never had any other wives even after the Fall nor did a number of his more immediate descendants. It was down a few generations before it even appeared. There may be symbolic significance in the first polygamist Lamech being descended from Cain (not to be confused with another Lamech, who descended from Seth).
Like divorce, it wasn’t supposed to be the case but only permitted through the hardness of our hearts. Keep in mind there were procedures for divorce in the Old Testament.
Christianity is about redeeming what’s been corrupted. The whole of Creation. Supporting polygamy, no-fault divorce and anything other than the original design of marriage goes against the spirit of redemption.
Early Christian thinkers like Iranaeus and Justin Martyr condemned polygamy. You can argue they probably ‘captured’ the spirit of Christianity on this matter better than us.
Christians are New Testament people. Our relation to the Old Testament isn’t similar to that of Israel, which has a branch of theology covering that. The New Testament favours monogamy over polygamy.
A comparison between marriage and Christ and His Bride, the Church is made. Singular not plural.
For the husband is the head of the wife even as Christ is the head of the church, his body -Ephesians 5:23
“Therefore a man shall leave his father and mother and hold fast to his wife, and the two shall become one flesh.” This mystery is profound, and I am saying that it refers to Christ and the church. -Ephesians 5:31-32
Individual Christians aren’t ‘married’ to Christ. Collectively, we are in essence cells, organs and limbs that form one Body. One Bride. One Church.
For just as the body is one and has many members, and all the members of the body, though many, are one body, so it is with Christ…that there may be no division in the body…Now you are the body of Christ and individually members of it. -1 Corinthians 12:12,25,27
To have more than one wife is to say there is more than one Church. Two or three wives don’t form one wife. They are not limbs and etc. of one wife but are individual people.
And no, different denominations does not mean Christ has multiple brides but the Bride has been gravely injured and we pray for healing and unity in the present time, which will be perfected when Christ returns. We see this in Revelation. Even Jesus prayed:
I do not ask for these only, but also for those who will believe in me through their word, that they may all be one -John 17:20-21
Also consider:
This mystery is that the Gentiles are fellow heirs, members of the same body, and partakers of the promise in Christ Jesus through the gospel. -Ephesians 3:6