The altar and the sacrifice of the Mass are Sacred tradition, but the sacrifice of the Mass is not a guilt offering or a sin offering, but a thanksgiving offering and a thanksgiving offering is one that can still be offered even in these last days, after God Himself came to save us from our sins. The first possible day for the Apostles to worship God in the temple by means of a thanksgiving offering, after the sabbath, is the same day we have always worshipped God, the Lords day. And if there is a day which is set aside for man to worship God especially, it is natural, traditional and good that we should do it together. It is as necessary as the third commandment. It is also a precept of the Catholic Church.
Furthermore, the custom of altars and the priesthood and the liturgy is one of man's universal customs. (As is abolishing them)
When I asked for an altar, I was told that we needed none, for men our brothers gave us clear oracles and one creed in their universal customs and ideals. But if I mildly pointed out that one of men's universal customs was to have an altar, then my agnostic teachers turned clean round and told me that men had always been in darkness and the superstitions of savages. - GK Chesterton, Orthodoxy
And, if it is a universal custom to have an altar, priests, religion etc... then there's no real difference between the forms that Catholicism employs and it should all be cast off, because true Christianity needs to distinguish itself.
The religions of the earth do not greatly differ in rites and forms; they do greatly differ in what they teach. It is as if a man were to say, "Do not be misled by the fact that the CHURCH TIMES and the FREETHINKER look utterly different, that one is painted on vellum and the other carved on marble, that one is triangular and the other hectagonal; read them and you will see that they say the same thing. The truth is, of course, that they are alike in everything except in the fact that they don't say the same thing. ibid.
The truth is, true Christianity distinguishes itself by its teaching and, as the old song goes, by its love. In this way, the Mass is a traditional way of showing God that you care and you're paying attention (it's more than that, but it is also that).
Now, I must go and make my wife a waffle, because I love her an I am paying attention.