I just don't buy this idea that Mary stands between me and Christ, that His grace comes through her to me, like she is an aqueduct. This seems to be the traditional idea of "mediatrix" but it just seems excessive. I agree with this docuмent when it says that God is the one who bestows graces through Christ. Directly to us, not through any intermediaries like Mary. She prays for us, but she doesn't stand between God and us, right? This traditional idea of mediatrix seems highly excessive. And I'm comfortable disagreeing with it because it's just theological opinion

Christ passes the graces through His mother inorder to increase her glory. The Blessed Virgin has received all graces possible for a creative to receive. Frankly it makes sense to me. She literally had God inside her, this is very special.

Fr Gregory Hesse speaks about this. The title of co-Redemptrix is not a dogma , but a traditional teaching.  He was hoping that the Church would one day define exactly what is meant by co-Redemptrix, because Our Lord is the Redeemer. The following concerns the Dogma of the Immaculate Conception but certainly sheds light on the role of Our Lady. Just think: if there would have been no Immaculate Conception , then there wouldn't be THE "merciful" Redeemer. 

https://www.papalencyclicals.net/pius09/p9ineff.htm

Pius IX: 
"...These ecclesiastical writers in quoting the words by which at the beginning of the world God announced his merciful remedies prepared for the regeneration of mankind — words by which He crushed the audacity of the deceitful serpent and wondrously raised up the hope of our race, saying, “I will put enmities between you and the woman, between your seed and her seed”[13] — taught that by this divine prophecy the merciful 
Redeemer of mankind, Jesus Christ, the only begotten Son of God, was clearly foretold: That his most Blessed Mother, the Virgin Mary, was prophetically indicated; and, at the same time, the very enmity of both against the evil one was significantly expressed. Hence, just as Christ, the Mediator between God and man, assumed human nature, blotted the handwriting of the decree that stood against us, and fastened it triumphantly to the cross, so the most holy Virgin, united with Him by a most intimate and indissoluble bond, was, with Him and through Him, eternally at enmity with the evil serpent, and most completely triumphed over him, and thus crushed his head with her immaculate foot.[14]

This sublime and singular privilege of the Blessed Virgin, together with her most excellent innocence, purity, holiness and freedom from every stain of sin, as well as the unspeakable abundance and greatness of all heavenly graces, virtues and privileges — these the Fathers beheld in that ark of Noah, which was built by divine command and escaped entirely safe and sound from the common shipwreck of the whole world;[15]