many of those who leave were never very good Catholics to begin with - they either were poorly catechesized and didn't understand the faith or were disgruntled about the moral demands Catholicism makes. Honestly, I'd prefer a smaller RCC if it meant that more of the members were faithful and practicing. Converts tend to be more faithful than "cradle Catholics" so tens of thousands of converts is something to celebrate.
Good point.
Many who stay are not very good Catholics either. We're counting heads here, not judging people's sanctity.
"Better that only a few Catholics should be left, staunch and sincere in their religion, than that they should, remaining many, desire as it were, to be in collusion with the Church's enemies and in conformity with the open foes of our faith." - St. Peter Canisius