I take the view that protests are a multifunctional tool for social change. Expecting a protest to "work" is like expecting an egg to make a cake.
Protests aren't for convincing politicians to do the right thing, they are for:
*grabbing media attention
*connecting disparate activist and advocacy groups with each other
*demonstrating public engagement
*helping people find joy and/or comfort in their movement
*disrupting the business-as-usual
*practicing how to work together in a large group for a unified purpose
Every protest I've been to (I've been to some) I've seen friends and colleagues mix with strangers, be introduced to each other, exchange pamphlets and contact info, people singing and laughing together (even for dire events), people learning how to act in solidarity together, people (including me!) seeing how policing works to maintain the status quo even when that status quo is bigoted, racist, ableist, colonialist, classist, and heterosexist.
Protests can do lots of things. They don't (usually) make politicians change their opinions. For that you need direct action and mass movements, both of which can arise out of public protest.