Anti-war demonstrations are a form of militant lobbying. Even radical direct action and civil disobedience aim to convince power-holders to do something different. This faith in government is misplaced.
There are two sides to this war. One is the war among imperial powers. The other is the war between the global capitalist class and the global working class. Both are heating up.
The NATO nations and Russia are all imperial powers. NATO wants to expand into Eastern Europe, and Russia wants to rebuild its empire. All the combatants seek to incorporate Ukraine into their economies at the expense of Ukrainian workers.
Socialism is the Best Medicine