Yes. But one must realize that “being in the Church” includes many people that are not formally Catholics, but who believe in sincere conscience only part of the whole teachings of the RCC. That includes many Protestants. But the FULLNESS OF THE TRUTH. is found only in the RCC.
This is as an inaccurate a statement as the one that the SLC brand of MormonISM makes - found on this plaque in Temple Square:
The fullness of the truth is only found in the Bible.
The flotsam and jetsam (debris) of the many false teachings clutter up the fullness of the truth so it is hard to find in Catholicism.
It is found easily in pure Christianity in the many gatherings of millions of born again saved Christians which is what makes up the true body of Christ.
Being a member of the body of Christ is a simple decision and commitment. It is a free gift that costs you everything.
Every member is a citizen of the Kingdom of God, no longer bound to this world.