A lot of people “uniquely” participated in the redemption.
Judas did, Pilate did too.
So did Joseph, and Simon of Cyrene.
That doesn’t make them co-redeemers, nor does what Mary did make her co-redeemer.
As I said I prefer it remain a personal devotion. Mainly because I think other Catholic Marian doctrines very cleary are evidence of God’s grace which are in time shared by all believers. We all will be made sinless, we all will one day be united body and soul with Him in heaven. As such proper belief in these doctrines gives Glory to Christ alone. But I think there is too much likelyhood for error and cultism developing from declaring Mary as coredemptrix official doctrine.
Mary did indeed cooperate with God’s plan for salvation and we should honor that. But it should not be elevated to where there is any possibility that it makes us forget that Jesus alone is savior and redeemer. Which I am afraid lacking firm teaching on the matter would too easily happen in a world too ignorant of Christ.
God had a plan and all the Bible characters were part of the plan. They were not the WHOLE plan but a part of it, as was Mary.