Leitourgia

Official, sacred, service, public, ministry.

From the NLM:

The liturgy is the Church’s public and lawful act of worship, and it is performed and conducted by the officials whom the Church herself has designated for the post — her priests. In the liturgy God is to be honored by the body of the faithful, and the latter is in its turn to derive sanctification from this act of worship. It is important that this objective nature of the liturgy should be fully understood. Here the Catholic conception of worship in common sharply differs from the Protestant, which is predominantly individualistic.

Objective, corporate, public vs. subjective, personal, private. An important distinction, to be sure, but one completely falsified through the employment of the party terms 'Catholic' and 'Protestant'. Nor are they mutually exclusive as when an 'objective' service is performed "in a tongue not understanded of the people": the resultant mass subjectivity, issuing in a host of private devotions, proves that. Note that our service may be prayed in English but also in Greek, Latin, or Hebrew, where those tongues may be understood, as in college chapels. (And, peradventure, isn't the new subjectivity the same as the old subjectivity?)

No, the difference between "common prayer" and the (other) world inhabited by Papists and Puritans is located instead in its embrace of certain tenets of the modern age (argument borrowed from here):

1. Anti-superstition, or a careful pruning back of an overwrought supernaturalism which saw human beings as daily subject to the malevolent or beneficial workings of highly active but completely unseen spirits. Accordingly, there is found in its pages no exorcisms and no invocations of saints.
2. Anti-authoritarianism, or a greater acknowledgement of individual liberty and self-determination that nonetheless avoids the other extreme of Anabaptist-style communism or radical egalitarianism. Tokens of this are the common cup and the repudiation of foreign interference.
3. Something else new that might be called Anti-fatalism,
   

Something else follows from this last fact, when combined with the other two. But that will be the subject of a different post.