Of course. My wife was a long-time Catholic (her maiden name was McNamara; guess how long her roots were in the RC church?) She has been through the temple many, many times.
If you viewed traditional Christianity as sufficient, you wouldn't be trying to "convert" us "gentiles" at all.
Actually, you nailed it. If "traditional Christianity" were sufficient, there wouldn't have been any need for a Restoration, now would there?
So obviously, we believe it is NOT sufficient to fulfill the divine plan that God has for each of His children.
Realizing this, many of us convert from our old, incomplete faiths and doctrines, and embrace the fullness of Christ's gospel.