Flirt with “modernity” however it may, Catholicism is still guided by Scripture and by two thousand years of accumulated wisdom, not necessarily in that order. Now which of these traditions, do you think, prohibits a gluten-free Eucharist? Both of them, apparently:
A great theologian of the Church during the 1200s, St. Thomas Aquinas, was one of the first Church theologians to describe clearly what valid matter is for the Eucharist: “Now among other breads, wheaten bread is more commonly used by men; since other breads seem to be employed when this fails. And, consequently, Christ is believed to have instituted this sacrament under this species of bread. Moreover, this bread strengthens man, and so it denotes more suitably the effect of this sacrament. Consequently, the proper matter for this sacrament is wheaten bread.” Accordingly, Canon Law specifies the use of wheat bread, stating that the Eucharistic species must include unleavened wheat.
It is possible, however, to meet the specifications of Canon Law — if not necessarily the requirements of the most severe celiac sufferers — with low-gluten breads for the sacrament.