There are only a few exceptions like Zoro vs Wano Samurai, Luffy vs Number giant, Sanji vs Page One and Luffy Red Roc vs Kaido.
Animation is not the only important factor, impact, futility and sound. Lucci vs Luffy had it all.
Animation is not the only factor, but I was talking about from a production as opposed to story standpoint. Its also worth noting that a good portion of episode 309 was fairly mediocre filler action.
And there are more than a few examples. There are tons of episodes in Wano which are immeasurably stronger from a production stand point which are fairly middle of the road episodes.
914 and 915, which are the first luffy vs kaido episodes, in terms of production values, blow 309 out of the water. Sanji vs Page One in 925 blows 309 out of the water. Zoro vs Killer in 933 and 934 are both much stronger episodes production wise than 309. Even fairly forgettable episodes in Udon liker 945 and 946 are better animated and put together than 309 despite not having as strong story beats or vocal performances.
I could literally list probably a dozen or so more episodes, but it doesn't really change my point.
Episode 309 had strong storybeats. Two excellent animation directors(Naoki Tate and Katsumi Ishizuka), and a solid highlight(the jet gattling on Lucci). It had a solid board, excellent voice performances, and some really solid OST in places. But its worth noting that most of the action in that episode was not very good, and there was also a lot of very mediocre filler action.
Its not a high bar to surpass, and even pre time skip, there are plenty of episodes which easily surpassed it(episodes in Thriller Bark like 369 and 377 come to mind, or in sabadoy with episodes like 404 and 405 among others).
Lucci vs Luffy is a great fight narratively, and had amazing performances, but I think holistically, when looking at it from a production standpoint, it wasn't a terribly strong climax or action episode in comparison to stuff that has come after.