I heard a priest once say that every heresy had a seed of truth within it that the Church could then sift out and properly nurture.
As for theological contributions, I cannot think of anything that isn’t rooted in the Faith of the Church anyway, but I will tell you this, as a Catholic raised Baptist, and after spending five years as an Anglican: your average, maybe even your slightly below average, Evangelical knows more about the Bible than your average Catholic. I think one thing that we should borrow from Evangelicals, at least, is the idea of Sunday School. From infancy to old age, Baptists (for example) have Sunday School classes where they study the Bible (though I think Catholics should include the Father’s, the CCC, etc, as well). I learned songs as a little boy that helped me remember the stories of the Bible (“Zaccheus Was a Wee Little Man”, etc.). We ought to do that for our children.
Protestant congregations generally sing better and while Protestants seem to have dropped the theologically meaty old standards (“On Christ the Solid Rock I Stand” and “There is a Fountain Filled With Blood”) for “praise” music, they have, by and large, avoided the puerile and banal “self-affirming-Jesus-is-my-12-step-sponsor” rubbish that we’ve been afflicted with for several decades.
