If you have to choose between being a competent musician and being a competent theologian when it comes to sung worship - choose a competent theological. But being a competent theologian should lead you to desire to grow in excellence in your musical craft.
Yes, leading worship is pastoral before it is musical. But music is one of the tools we use to shepherd-well the people of God. Whether that be through song choice, dynamics, or transitions.
When we do not seek to become the best musicians we are able, we begin to create distractions for those we are serving. Our inability becomes a hindrance rather than a help, enabling the people of God to sing and celebrate who He is and what he has done.
If this is describing the way that you lead worship - what can you do? Here are a few ideas to get you started:
Find free resources. Youtube has millions of tutorials. Find a friend to help give you feedback and give direction about how you could improve.
Get to the woodshed. Go ahead, spend an hour on a single part, a single piece, a single song. Work at it until it feels like your hands, legs, and throat couldn’t stand to play it one more time - and then play it one more time.
Build time into your schedule to practice songs. One of my work goals last year was to get better at memorizing my music. This meant that along with blocking out time for all of the things that were important to me during the week, I needed to find a few spare hours to work intentionally on the songs for any given Sunday, and the new songs that we would add to rotation - this was hard work and seemed less ‘important’ initially to me, but I was surprised how free I felt during sung worship to actually engage the songs and the people - without being conscious of the chord chart.
Listen to songs and artists outside your personal musical preference. Are there genres that you avoid, or have never considered? Familiarize yourself with the techniques, tones, and tricks of other musicians and genres. And return to what is familiar with a fresh awareness and musicality.
Not every musician will be a world-class musician. Not every musician is ready for a Nashville recording studio. But I do believe that every musician can work to hone and build their skill to the glory of God and the good of His people.