Even if the majority of Russians don't support the war, I think the kind of person who would be in a position to be able to take over Putin's position wouldn't be someone who would take the sentiment of the masses to heart.
This is what I'm thinking too. His replacement is going to have to win...
"Barely started" is the only way they could possibly justify their failure without admitting incompetence. The only alternative is dropping the strongman facade, they're backed into a corner in that way too.
This is a reasonable point. It's important not to think of this as Russia's war, but Putin's war, which I think most people do. Putin deserves all of the hate and humiliation he can get, but not Russia as a whole.