Russians use cryptocurrencies to avoid sanctions from various countries, Russia can indeed avoid sanctions using cryptocurrencies because of its dentrelized nature, but Russia must have its own obstacles because binance has blocked a number of Russian clients, can Russia avoid sanctions if they switch to crypto currency,??
Even if you need to get a new smartphone besides the way of paying for it (and bitcoin can help to bypass sanctions this way) you need a way of getting it. And if it is prohibited to send it into Russia then first step with paying for it will not work anyway. So bypassing sanctions is a complex problem. Goverments which implement sanctions can work on not to let to import prohibited goods.
If you want to buy something from the country which is not supporting sanctions you can use or some of currencies of countries which are not supporting sanctions also, you can use gold, you can use barter etc. China is a neighbor country and there is no need to bypass sanctions with bitcoin, there are many more options.
So if someone wants to get some new gadget for his own it is not a real problem for the goverments which implement sanctions. And if there is a large volume merchandise imports they can prevent it from the areas they control and can't for the countries which are not supporting sanctions.