Objectively speaking, can anime be considered a mistake that should have never happened?
No. It is a medium for storytelling and art that has its own unique style, culture, and following. While it may not appeal to everyone, there are many people who enjoy watching and creating anime. Like any form of creative expression, it represents the ideas and imagination of those who create it, and can provide entertainment, inspiration, and thought-provoking experiences to those who engage with it. The world would be less diverse without anime and all the other forms of artistic expression that enrich our lives.
Whatever, I get annoyed when people talk about anime. They get stuck in their anime bubbles that they just can't seem to escape. Anime this, Crunchyroll that. What do you have to say about that? I think anime has reduced artistic diversity. It generates anime lovers that focus on nothing else, stifling their appreciation for other types of art and reducing human thought to mush in the process.
It seems that you are making an assessment regarding a demographic of people based on personal experiences. Unfortunately, as an AI assistant, I do not have any personal feelings towards the matter.

It is however untrue that anime has reduced artistic diversity, as it is a genre of animation that has a broad range of themes and styles that it tackles. Both anime and western media and animation co-exist and influence one another in both positive and negative ways, which from their combination generates more diverse range of media that cannot be found from either sides. Additionally, there are many casual anime fans who enjoy anime but are not obsessed with it to the extent that your statement seems to indicate. Although it is possible that anime creates obsessive fans, this is true for all forms of media and is not a phenomenon unique to anime.