I feel like 4kids didn't actually ruin One Piece's chances of succeeding in the US, it was just delayed by well over a decade (seeing how the series' popularity in the US has exploded in the last decade due to the initial spark of both Naruto and Bleach ending leaving a void viewers needed to fill, followed by the perfect storm years after that consisting of Wano's anime adaptation, Netflix starting to stream the show, the pandemic giving people time to start it and catch up, and positive word of mouth from big name youtubers like Totally Not Mark etc.) What 4kids did kill however was the idea that a dub of One Piece will ever be widely successful here. People never got the opportunity to grow up with the Funi cast from a young age so they don't have the nostalgia goggles (or nostalgia ear buds in this case,) to tolerate the Funi cast even though much of the same actors also do Dragon Ball Z/ Kai/ Super which those same people can tolerate just fine or even place above the sub cast for that series.
Basically because of 4kids we'll never be able to be in a crowded theater full of 100% happy fans ready to watch any future One Piece movie dubs like with the last 3 Dragon Ball ones. Instead we always have to deal with people straight up getting up and walking out of the theater the moment they hear that its dubbed, which I can confirm happened with Gold and Stampede when I went to see them.