Why did the Church say that an entrance hymn (like the Protestants have) is better than a Gregorian introitus nowadays?

When I attend Mass we sing an entrance hymn. There is no Gregorian introitus. In the Novus Ordo Missae we seldom have the Gregorian introitus. I've been thinking why the Church has a need to do away with the introitus. The only reason I can find is that people nowadays probably think that everyone must sing along or otherwise they are not participating. It is what I have been told. But I am interested in what the Church actually says. Why did the Church say that an entrance hymn (like the Protestants have) is better than a Gregorian introitus nowadays?