They aren't the Pope so that they don't speak for the Church. What they have to say is of little consequence in the grand scheme of things. There will always be some that disagree and think they know better than the Pope. I will say this, some of the concerns by the Traditional Catholics are valid. IMO, ecumenism has gone way overboard with some of the Catholic clerics.
As for church growth, you fail to mention that the annual growth rate for the Southern Baptist Convention, a predominantly conservative evangelical denomination, is only slightly smaller than that of the Roman Catholic Church.
Slightly smaller? Hmm...the Roman Catholic Church has now slightly over 67 million and the Southern Baptist Convention has 16,439,603? What math are you using to come up with that?
OTOH, there is a drift of liberal Roman Catholics to Episcopalianism, which may explain the growth of that denomination in contrast with the losses experienced by other mainline bodies, and a movement of conservative Episcopalians to Roman Catholicism.
I know nothing of this "drift" of liberal Roman Catholics to the Episcopal church. Can you show documentation supporting that claim? If true, then I'm glad they left and went to where they belong. We don't need naysaying liberals in the Church trying to corrupt it with liberalism. I will, of course, pray for conversion of their hearts back to the Church.
With regard to growth of different church bodies, please note that I was speaking about annual growth percentages, not raw numbers. The article you previously cited dealt with annual growth rate among the 25 largest Christian bodies. With a base of 67 million vs. 17 million, the raw numbers of Catholic increase will be about fourfold that of the Southern Baptists, though the growth rate is similar. Additionally, over half of the megachurches listed in a recent survey of the most influential congregations in America were either non-denominational, such as The Potter's House in Dallas, Texas, or associated with a small denomination, such as Coral Ridge Church in Fort Lauderdale, Florida, affiliated with the conservative Presbyterian Church in America, with denominational membership at about 350K. A lot of church growth exists beyond the range of the larger Christian bodies.
As for the drift of liberal Catholics to Episcopalianism, this observation is based on statements of current liberal Episcopalians as to their faith background and why they left Roman Catholicism, often because of Catholic opposition to homosexuality, abortion, etc. The reverse flow of conservative Episcopalians is based on personal observation, including old family friends who "swam the Tiber" 20 years ago when the liberalism in that denomination was too flagrant, as well as the existence of an Anglican usages group within the Roman Rite.