No, we are not supposed to make up our own translations of the readings of the Lectionary. There is, however, some looseness in adapting or translating the readings for use in children's Masses. And, apart from the readings, there are places in the liturgical rites where the celebrant or minister is given a choice of prayers, told to invite, introduce or use other suitable words, without any specific formula being given.
Concerning the problem you raise about readers changing words, R. Kevin Seasoltz says in New Liturgy, New Laws (The Liturgical Press): "If observance of a law occasions the rejection of the liturgy or the Church by a large segment of the community, surely the traditional teaching of epikeia justifies the non-observance of the law. This affirmation is in keeping with the medieval axiom that sacraments are for people; people do not exist for the Church. For example, in communities that are aware of and committed to efforts to assure justice for women and minorities in the Church, the use of sexist language in the liturgy is often both irritating and alienating: In some instances it arouses deep hostility.
"Sometimes the bias against women is built into the vernacular translation but not into the original Latin text. There is no reason why the words 'pro multis' in the text of [eucharistic] institution within the anaphora need to be translated 'for all men.' To avoid harm and insult to the community, ministers have rightly changed the text and avoided sexist language."