> Every dead Russian invader is a Ukrainian life saved.

No. Russia will just replace them. Or it bleeds white, which raises the risk of nukes.

To reduce lives lost (on both sides), either Ukraine or Russia needs to actually start winning with maneuver / tactical warfare, rather than WWI style positional warfare.

To win with maneuver warfare, Ukraine needs more equipment (tanks, planes, etc). This is how they won the Kherson counteroffensive (with a ton of ground taken and Russian heavy equipment destroyed). You don't need to kill the enemy, if you can overrun their position and force them to surrender. Russian had about 2-3000 lives lost which is a far more acceptable price than the hundreds dead every day in Bakhmut (where it's a WWI style battle with thousands dying to conquer a few metres of ground).

As for Russia, they've tried to win with maneuver warfare but it's hard to do this with incompetent command and Ukraine's extremely gutsy defence.