Usually when we talk about "fandoms" we're mostly talking about a specific group of people within a fanbase rather than the series itself, so for example:
Naruto fans would do this thing where they would bash on anyone who didn't read or watch the series, while at the same time putting down other animes or mangas that would be compared to it. So not only would this fanbase have issues within their own community, they would also bring outside fanbases into the mix and start drama with them. This was not only seen as very toxic but also very one dimensional because this would also assume that most Naruto fans were not very diverse when it came to anime.
But, I've come to the realization that the One Piece fandom is far worse, because unlike with the obvious boasting of your own favorite series, or even putting other fanbases down, this community is full of elitists. They see no flaws in Oda's work. They praise the author no matter what. They constantly bash and get defensive when a low point is called out in the story, and even think that One Piece is seen as the best of all time. At least in the previous Naruto community you would have people calling out shit for what it is, even if there were huge fanboys or fangirls of certain characters. No constructive criticisms from the OP community other than "this chapter was great or good" which not only portrays this community as dry but also unenthusiastic, but this is partly the fault of the way the story has been going, which has not been very good.
*A lot of people like to include the DBZ fandom, but let's be honest, most of them are a bunch of idiots, not ever to be taken seriously, when they think the likes of Goku is a "well written character" then there's really no discussion to be had.