I'm not normally a prologue person, but I did employ an extensive one in Errant, and I still stand by that decision.
A lot of prologues in Fantasy stories, I hate because they set up no tension. You know, it's all "long ago, the humans and the dragons lived in peace, but then there was a great war and the dragons were sealed away, but maybe magic will return to the kingdom..." and then we cut to protagonist waking up and going about his day. There was no reason to establish that magic came from a great dragon war or whatever because it doesn't really affect how that magic will impact the characters.
I chose to put in a prologue in Errant after deliberation because I've tried to write the story without one, and it's worse. Originally, we opened with Rekki as this grouchy, burned out adult knight (basically the person she is from chapter 1 onwards) then we bring up that she has this estranged childhood friend when Sarin is reintroduced, and there was then this series of flashbacks briefly getting across that Rekki used to be this wide eyed girl who wanted to be a knight and she had this super-great friend and stuff. I decided that like with the opening of Firefly, the sense of loss is stronger as well as your feeling of attachment to both Rekki and Sarin if you're first introduced to the more likeable Rekki, the kind girl with innocent dreams of being a hero, and this great friendship she had.
In the pre-reboot comic, Fan Dan Go, nobody really cared that much about Sarin, she was just kinda there like "yeah, she seems nice", but in Errant, people have very strong feelings about the unjust way she was treated and they're wondering where she is and excited to see her return.
Firefly and Fullmetal Alchemist to me show that sometimes a prologue can work. The key is that it has to matter. It has to depict a past (or future) event that had a massive impact on something directly and immediately relevant to the characters in the present and show some kind of interesting contrast or symmetry. I'd definitely say that the prologue of One Piece doesn't work, like nothing at all really changes if you don't have Luffy eat the gomu gomu fruit as an adult (it's still the kind of thing he'd do) and immediately go on his adventure. He did nothing at all and didn't really change in the years between the prologue and main story so it's unnecessary. The stuff with Shanks could have been left for when Shanks became relevant, many many years of updates later, and filled in with a short flashback montage.
So I'm not on team "no prologues ever", but I'm also of the opinion that you shouldn't put one in unless you genuinely believe it's the best way to impart immediately vital information by depicting events that definitely had to happen in the past for the story to work, and ideally you should see if it works other ways first. There's often a better way. It's possible in the future I'll regret my decision to do a prologue, but at the moment, I still feel like the alternatives were all worse for Errant specifically.