Jungle warfare is the way to go, anything conventional is doomed to fail. However, Russia has no regard for the people of Ukraine. They don't care about civilian casualties. They don't fuck around. Surrender or be killed is their approach. Hence why they have to take the fight to Moscow. Snipers would be beneficial.
Russia cannot hold Ukraine without civilian cooperation, bombing them out of existence means they will end up holding a wasteland while their economy craters - that's hardly their agenda here and is unsustainable even in the short run.