First, even if you lived a wretched life, the preacher shouldn’t lie about that. Maybe they should tell us the truth. Maybe the best thing we could hear is that you were a rotten person. Maybe we should make it a goal to live as exemplars of virtue, rather than as warnings against vice.
Second, the proper focus of a Christian funeral is God, not the deceased. A death is only the occasion for gathering. A Christian funeral is a service of worship. We hope we can give thanks for the person who has died. Sadly, there are cases where this is very hard to do.
Third, if you live in such a way as to be remembered by others as a “good” person, I do not want to dismiss the positive outcomes that could result from such an aim. But beware. We do good things all the time from bad motives. It would be better to live for the glory of God, realizing that all is a gift, than from a self-aggrandizing motivation.
Fourth, at a bare minimum, the truth that should be told at a Christian funeral is the truth of the gospel: Christ has died, Christ is risen, Christ will come again. That is why we can grieve, but not as those who are without hope.