Showerthought: My French press bitterness problem led to a brewing experiment

My French press coffee was always too bitter, and I couldn't figure out why. On one hand, I read that a super coarse grind is key to avoid sludge. On the other, some friends swear by adjusting the steep time instead. I decided to test it myself by trying different grind sizes with varying brew times over a week. I found that a medium grind with exactly four minutes of steeping gave me the smoothest cup. It was a simple fix, but it took some patience to nail down. Now I wonder which factor really matters more. What do you think? Is it all about the grind, or does timing rule your brew?