Mark Shea wrote a valuable two-part essay last year on the relationship of the Catholic Church and Islam - specifically in relation to the teaching of the Catechism that Muslims "profess to hold the faith of Abraham, and together with us they adore the one, merciful God, mankind's judge on the last day" (CCC 841).
I will concede that this was something of a stumbling block on my way into the Catholic Church, but upon further reflection I don't really see the scandal anymore. No Christian is going to pretend that Muslims have a complete doctrine of God, since they deny the Trinity. But Muslims aren't the only ones doing that: Judaism denies it as well. If you're going to say that Muslims don't worship the same God that we do, it seems to me that you're going to be obliged to say the same thing about Jewish folks, and for the same reasons. And I can't imagine that there's anything controversial about saying that Jews worship the same God as we do. "For I bear them witness that they have zeal for God, but not according to knowledge" (Rom. 10:2).
So anyway, I eventually figured out that there is nothing "modernist" about this portion of the Catechism. But Mr. Shea goes a bit further and (among other things) points out that this perspective is nothing new in the Catholic Church but rather dates back as far as the 11th century.
The essay is worth reading. It starts here and concludes here.