Jonathan Edwards commented on the doctrine in the Trinity, " And God has appeared glorious to me on account of the Trinity. It has made me have exalting thoughts of God, that he subsists in three persons; the Father, Son and Holy Ghost. The sweetest joys and delights I have experienced, have not been those that have arisen from a hope of my own good estate, but in a direct view of the glorious things of the gospel"
I love that, but let me draw your attention to one thing. Edwards connects the doctrine of the Trinity with the "glorious things of the gospel". This doctrine is a sidebar, not theological mumbo jumbo - it is an essential part of the life giving, beautiful gospel.
Is the doctrine of the Trinity relevant? I don't know. Is the gospel?! You better believe it is.