you are likely correct that the aim of sanctions was never to get Russia to back down. indeed, making the war more painful only makes it more necessary for Russian leadership to exit the war with something resembling a clear victory. If your aim is to stop "Russian imperialism", then you should attack it where it could be its weakest: justification. The U.S.-led west has done the opposite of that, delivering justifications for Russian military action as if they want it to happen-- a fact that only manages to go unrecognized in the media markets that they control. Maybe they do want it to happen; the existence of bogeymen is a wonderful buttress to existing authority. In any case, the suffering isn't real to the people making the decisions and it shows.
If sanctions were designed to hurt average Russians, Russia would be under very different sanctions.
An aim of war is to degrade the opponent's ability to fight: sanctions are in this context more about impairing a country's ability to continue fighting by restricting its access to finance, equipment, industrial materials and skills/knowledge that would assist its war effort. Indeed, Russia is still largely free to import goods for the maintenance of its people's general welfare: for instance, Russia is allowed to import goods for the maintenance of major civilian infrastructure, such as its energy generation. Inevitably, wider economic damage suffered by Russia will adversely affect its population, but sanctions have been designed to avoid specifically targetting the general population. Sanctions have targetted the international interests of Russian elites, but they are having to give up superyachts, foreign mansions and Rolexes, not food, medicine and heating.
And of course, by contrast, Russia has had no compunction about destroying Ukraine's civilian infrastructure. One might note, for instance, the particularly aggressive attempt to wreck Ukraine's energy network during the onset of Winter, threatening to cause its people enormous hardship and risk to life.
