David, there are some beautiful hymns in the LSB that are not ancient. Three examples: Thy Strong Word, The Lamb, What is this Bread. One of my favorite things to sing is in the Order of Prayer and Preaching. It is the Old Testament Canticle, absolutely beautiful!

Sadly, most "modern Christian" music does not reflect Lutheran doctrine. May I suggest you read the Fire and the Staff by Klemet Preus. It may help you with your struggle.

God's blessings to you. I pray you find the peace you seek.