Navalny may not be perfect but in my eyes he's a hero. He's put his life on the line all these years to challenge power. There's not many people who would go so far to stand for their principles.
Habeas corpus. It's a really simple principle of justice and a test of self rule. It's disappointing to see the Russian people cede power to such corrupt rule.
Power comes, everywhere on our planet, from owning and maintaining the monopoly on violence. Which is vested in the military and police. As you rightly point out, going against those is nigh impossible.
The comment you replied to does not refer to WWI nor Russia's war with Ukraine, it refers to the Russian Revolution after WWI. It sarcastically indicates that "nothing" can be done now about the unjust state of Russia resulting in Navalny being a political prisoner.
The comment you replied to refers to the Russian Revolution after WWI. The damage inflicted by WWI greatly damaged the Tsarist regime. (And, no war, no German government shipping Lenin back home.)