The Liturgy of the Eucharist is a sensitive area:
25. The whole life of the liturgy gravitates in the first place around the eucharistic sacrifice and the other sacraments given by Christ to his church. (SC 6) The church has the duty to transmit them carefully and faithfully to every generation. In virtue of its pastoral authority, the church can make dispositions to provide for the good of the faithful, according to circumstances, times and places. (Council of Trent, Session 21, Chap. 2, SC 48ff, 62ff) But it has no power over the things which are directly related to the will of Christ and which constitute the unchangeable part of the liturgy. (SC 21) To break the link that the sacraments have with Christ, who instituted them, and with the very beginnings of the church, (Inter Insigniores 107-108) would no longer be to inculturate them, but to empty them of their substance.
This might go without saying, but there is still concern about the occasional fringe element that suggests raisin bread or grape juice, or jokes about pizza and beer or donuts and coffee. No serious liturgist even thinks about substantial changes to the Liturgy of the Eucharist. And most serious adaptations proposed, such as substituting rice flour for wheat, or mustum for wine, involve an understandable outreach to those who suffer because of the “accidents” of the substance involved.