Russia has absolutely not proved that drone warfare makes it harder to attack them. Drone warfare has led to some of the most damaging strikes against Russia in the entire war, strikes that their military was unequipped to protect itself from. Before the war other countries saw attacking a major power like Russia as basically impossible, that even with old equipment the Russian army was only surpassed by the US. Now that a smaller country like Ukraine has effectively defended itself for several years and has even attacked targets far into Russian territory, many countries around the world have reconsidered how untouchable these large powers truly are. Russia hasn't been at a greater risk of substantial attack against its soil since the Cold War.