It would be disingenuous on our part to accept that which lacks the fullness of truth.
So why have Catholics downplayed the blood of Christ?
We don't and never have. The Body, Blood, Soul and Divinity of Christ are fully present in both species.
1364 In the New Testament, the memorial takes on new meaning. When the Church celebrates the Eucharist, she commemorates Christ's Passover, and it is made present the sacrifice Christ offered once for all on the cross remains ever present.183 "As often as the sacrifice of the Cross by which 'Christ our Pasch has been sacrificed' is celebrated on the altar, the work of our redemption is carried out."184
1365 Because it is the memorial of Christ's Passover, the Eucharist is also a sacrifice. the sacrificial character of the Eucharist is manifested in the very words of institution: "This is my body which is given for you" and "This cup which is poured out for you is the New Covenant in my blood."185 In the Eucharist Christ gives us the very body which he gave up for us on the cross, the very blood which he "poured out for many for the forgiveness of sins."186
1366 The Eucharist is thus a sacrifice because it re-presents (makes present) the sacrifice of the cross, because it is its memorial and because it applies its fruit:
[Christ], our Lord and God, was once and for all to offer himself to God the Father by his death on the altar of the cross, to accomplish there an everlasting redemption. But because his priesthood was not to end with his death, at the Last Supper "on the night when he was betrayed," [he wanted] to leave to his beloved spouse the Church a visible sacrifice (as the nature of man demands) by which the bloody sacrifice which he was to accomplish once for all on the cross would be re-presented, its memory perpetuated until the end of the world, and its salutary power be applied to the forgiveness of the sins we daily commit.187
1367 The sacrifice of Christ and the sacrifice of the Eucharist are one single sacrifice: "The victim is one and the same: the same now offers through the ministry of priests, who then offered himself on the cross; only the manner of offering is different." "In this divine sacrifice which is celebrated in the Mass, the same Christ who offered himself once in a bloody manner on the altar of the cross is contained and is offered in an unbloody manner."188
It's been awhile since I've been to a Catholic Mass
While there it sounds as if you weren't paying attention during the Eucharistic Prayer.
... so have to think the use of unleavened bread isn't an ancient requirement.
You think incorrectly. Unleavened bread was used at the Last Supper.
From my POV, your "truth" is a lie.
In this divine sacrifice which is celebrated in the Mass, the same Christ who offered himself once in a bloody manner on the altar of the cross is contained and is offered in an unbloody manner.
Unbloody blood?
While there it sounds as if you weren't paying attention during the Eucharistic Prayer.
I must have been too busy wondering where the little glasses were & why the priest drank all of the wine himself, while y'all were only given bread. (I think that's been changed since I've been to a Catholic Mass.)
You think incorrectly. Unleavened bread was used at the Last Supper.
I think the Orthodox & Oriental Churches disagree.