It may be decentralized, but it does have a shared slogan (which is repeated and amplified by individuals and organizations affiliated with the movement), and it does have an agenda expressing their ideology. BLM deleted the "What We Believe" page once it became controversial but you can find a copy of the original online (https://uca.edu/training/files/2020/09/black-Lives-Matter-Ha...). You can also see the "13 guiding principles" that are commonly adopted and implemented by institutions like schools (https://www.blacklivesmatteratschool.com/13-guiding-principl...) or the NEA (https://www.nea.org/advocating-for-change/new-from-nea/black...), which is the main teachers' union in the US and also the largest labor union in the US. Even if there are many organizations and actors, the widespread and uniform adoption of their agenda resembles the long march through institutions (https://en.wikipedia.org/wiki/The_long_march_through_the_ins...), and is turning our institutions into channels for indoctrination (https://www.theatlantic.com/ideas/archive/2021/03/should-bla...),

Also tellingly, they are far from an organization focused on just policing equality, which is ostensibly where BLM began. If you look at the latest updates on their website (https://blacklivesmatter.com/blm-demands/), you'll see them advocate for various explicitly political goals aligned with the Democratic party, such as wanting Trump banned from digital platforms (censorship), wanting to expel legislators who challenged election results (violating their political rights), and more. The 13 principles and "what we believe" manifesto I mentioned above also encompass the vast majority of the progressive political platform rather than focusing on the policing issue.