"Christianity" is open to all. Certain sects, churches calling themselves Christian, make exclusive regulations and set certain standards. One person in an Italian city pronouncing measures that are supposed to apply to all Christians is not "open", it is absurd. If a Christian wants to know how to be a Christian and what to do, prayer and communion with fellow Christians is the prescribed action. Dictates from afar are arguably against the individual responsibility that Christ pointed out.
Of course, if we are not truly Christian, then anything goes.
My interest lies in history--including etymology. You noted that Catholic means "universal". "Universal" comes from Old French, and Old French was spoken between the 8th and 14th centuries. It is thought "universal" popped up around the 12th century. Meanwhile, Catholic was in use over a thousand years before that. The word closest to "universal" in Latin meant One. I find this interesting because of Jesus' own prayer--that his followers would remain One just as he was One with the Father.
This is why I consider history vital. Instead of modern day people insisting Catholic was applied because someone in the 12th century was being tricky, we learn what was in the minds and hearts of Jesus and the first Christians. The Catholic Church, from the first, has maintained and protected Apostolic traditions and passed them on.
Meanwhile, Protestants began insisting that people could read the Bible and the Holy Spirit would teach them what it means. Voila! New teachings began cropping up, with the claim, "Look it says this in the Bible, and clearly this means that..."
Not even the Catholic Church is immune to changes in language and culture which is why I believe each individual does well to, at least occasionally, brush up on the language, history, and culture of biblical and apostolic times.