Horses for courses.
If you want to make song in a folk tradition or a country one, you can find out most of what you need to know musically (leaving out lyrics) by learning half a dozen songs well. By that stage you should see a commonality about those tunes that can inform your own compositions. Three or four time signatures, the relationship of tonic, dominant & subdominant chord structure, maybe a relative minor etc. Add two or three scales for melody, and you are set.
You don’t need a 12 tone matrix chart, know chord substitutions or have any truck with 5/4 time.
As Horras said in post #20 (where is he? One great post and he’s gone!). Theory is best thought of as a tool. A tool is made to do a specific job. A watchmaker has no use for a band-saw, and a shipwright doesn’t need any pruning shears.
So if you need a make use of theory it should be with some notion of what it’s for; otherwise you may as well be a museum curator.
I see theory as a tool shop. You make your choice according to need.