I made good brussels ONCE. I have the recipe and tried to do it many times, never could make them good again, always too bitter. I know it’s possible but I’ll wait a decade for stars to align again.
Brussel sprouts literally have become less bitter over the last few decades, but depending on where you get yours they might still be using older variants. Maybe try a different source?
I literally just clean mine, cut them in half & remove stems, toss them with olive oil & salt & pepper, then roast them cut-side down. Perfect every time.