Yeah! Yeah! If you actually asked the Black Lives Matter activists whether all lives matter, they would agree. But the “All Lives Matter” slogan is just a way of hiding the message that the Black Lives Matter activists want to put across: “We have noticed that no matter how much it does protest, this society treats Black people inferior to others in matters up to and including lethal force”.
You can criticise the slogan “black lives matter” for not saying “black lives matter is much as white lives” (or similar). But it’s a slogan not a manifesto, and slogans are never as accurate as they could be – it’s in the nature of using few enough words to be catchy.
Personally I think that the BLM campaigners over-estimate the problems of racism and under-estimate the problems of economic disadvantage (which applies to all ethnic groups). People with poor parents are less likely to do well than those with rich parents; and yes exceptional people will do well regardless.