I agree that the slogan 'all lives matter' isn't the right slogan, but I don't think "black lives matter" or "black+indigenous lives matter" are the best slogans either, if people want this movement to go far. It gives the impression that it's a movement for only black or indigenous people, and if the movement is about getting better treatment and recognition for those groups, the slogan works.I know the answer will be that people should already know that the movement doesn't cover only those people, and yes that's true they should, but 'should' doesn't equal 'is'.
For a more broader movement against racism and to get everyone involved it should be something like 'racism matters' because in the end the issue is racism in general. I went to the vigil myself, and noticed that the vast majority were black or white, but over 30% of the city is made up of 'brown people' like myself. That tells me the movement still needs some tweaking.