I’m puzzled, too. If Matthew 19 means what it appears to say, then divorced and remarried individuals are continuously committing adultery. So the adulterers are probably the ones who need to do something redemptive, I’m guessing. The adulterers would be the “they.”
Our Redeemer can redeem them, but not while they continue in adultery, surely? Surely they would need to cease their sin and repent. That must be what is meant by “something redemptive.”
It’s not really clear from the post, but surely that is what was meant.
I guess I’ll wait until aMPU provides more explanation. I too thought “they” meant the adulterers, but maybe aMPU meant the Church?