Edit1: Decide to change ‘by’ from Thin Lizzy to the The Dubliners.
As stated by @Semi-Hemi-Demigod@kbin.social, it’s not written by Thin Lizzy but in my view it was the inspiration to the Metallica cover. Even though The Dubliners are ‘credited’, it’s a old tradicional song.
Having listened to Irish folk music from the Clancy Brothers to Christy Moore to the Pogues for the past 50 years, you’re absolutely right.
But the Thin Lizzy version wasn’t bad.
Absolutely, their version is a certified banger. But they didn’t write it.
Also, you’ve got great taste in music