Is the Eucharist necessary for salvation?
Normally, the faithful reception of the Eucharist is important for salvation for those who have reached the age of reason, as Jesus makes clear in John 6:
The Jews then disputed among themselves, saying, “How can this man give us his flesh to eat?” So Jesus said to them, “Truly, truly, I say to you, unless you eat the flesh of the Son of man and drink his blood, you have no life in you; he who eats my flesh and drinks my blood has eternal life, and I will raise him up at the last day. For my flesh is food indeed, and my blood is drink indeed. He who eats my flesh and drinks my blood abides in me, and I in him. As the living Father sent me, and I live because of the Father, so he who eats me will live because of me. This is the bread which came down from heaven, not such as the fathers ate and died; he who eats this bread will live for ever.” This he said in the synagogue, as he taught at Capernaum.
The Church further confirms this foundational teaching in CCC 846. And yet the Church differentiates between those who knowingly reject Christ and his Church with grave culpability and those who don’t (CCC 847-48).
Thus, the Church summary are: the Eucharist and other sacraments, starting with baptism:
The Lord himself affirms that baptism is essential for salvation. He also commands his disciples to proclaim the gospel to all nations and to baptize them. Baptism is essential for salvation for those to whom the gospel has been declared and who have had the possibility of asking for this sacrament. The Church does not know of any means other than baptism that assures entry into eternal beatitude; this is why she takes care not to neglect the mission she has received from the Lord to see that all who can be baptized are “reborn of water and the Spirit.” God has bound salvation to the sacrament of baptism, but he himself is not bound by his sacraments (CCC 1257, footnotes omitted).