The main things that this special entails is overall good animation, callbacks, and iconic moments from One piece plus some cute moments.
As to why the animation is not perfect is due to some ugly still shots of the marines but overall the animation is smooth and looks fairy tail like and easy on the eyes. This special really highlights how other characters in One Piece sees the main crew and other great figures in the One piece world as well and why they Admire them, there are different reasons for different individuals as well which makes it more interesting and nuanced. And the two main characters who has the most love put in them are likeable and enjoyable to watch as well because they contrast well with one being a naive girl and one being a war torn Marine so you do not have to have watched One piece before to enjoy this experience.
However because of this, the episode splits to too many different perspectives which makes most of the characters existence about glazing someone else instead of developing their own story or moments. It is not all that bad though because the characters that we follow the most reinforces their own character by taking inspiration from notable characters of One piece. so the director made the best out of this problem. It still does not mean I would enjoy the story more than a story that focuses on characters who develop from their own experiences and connections instead of them having their character being about only being a "x" fan. Especially when the run time only is 24 minutes, and yes the purpose of the episode is to celebrate one piece and its cast. But it actually makes or breaks the story and is why there is so much disparity between One piece fans and bystanders who watched the special, because One piece fans love the glazing, and some bystanders hate it because they have not grown to like the ones being glazed. Not as if its the entire reason behind the disparity but it is a big part since it also spreads out the potential scenes for characters to have their own agency in the plot.
In contrast, it is a lot more clear that the OST is as good as it has always been, the music both new and old fits the scenes very well. Especially the new music tracks that was made for the brothers and for the finale for the atmosphere. By the way the finale was amazing for what it was and really tied this mini story together by using what we know about the plot and the characters with the ost blasting full swing.
So it was a pleasant experience overall, I do not advice watching this if you hate One piece but if you are neutral or like One piece it is a good to great watch.