Perhaps the most important lesson for Putin is the realization that he cannot rely on the military’s assessments of its readiness, forcing him to take a more direct role in overseeing strategic operations. Ultimately, the combination of strategic lessons and a battle-hardened force will make Russia more lethal on future battlefields.
Not even just battle hardened, they basically invented a new kind of warfare. I bet in a few years we'll start seeing drones be used in other conflicts just like how Russia and Ukraine have been using them, flying cheap drones directly into armor and chasing people down.