One Piece's biggest issues right now is usually these.
1. 'It's too long.'
2. It's popular and most newcomers have now gotten in at a point where two of the big three ended. (I'd say most entry level anime/manga fans are getting in via Attack On Titan, MHA, Demon Slayer etc) So don't understand why the big three were popular.
3. It's popular so it's 'fun to hate' it.
Other than length it's not really something that can be helped. The Anime definitely needs a One Piece Kai at some point.
The series itself is an investment which most casual anime fans just don't want to bother with when they can watch about 50 other series using the same time.
I totally agree! A One Piece Kai is desperately needed because of how long the series is and with the slow pacing. It can happen because of how popular the series is in Japan so that could be to the US's benefit