Yep, US sanctions were working in the past, when US economy dominated the world. Right now sanctioning a country just means that you are giving China a free reign over it.
It also helped in that past that if a country stopped doing whatever it was that drew US sanctions the US would lift those sanctions.
Take Iran. The US and several others sanctioned them over trying to develop nuclear weapons. Iran stopped the weapons program, agreed to inspections to verify compliance, and the sanctions were lifted.
Then the US put back sanctions for domestic political reasons, and so now when Iran does something the US does not like (such as supplying Russia with weapons to use against Ukraine), the US doesn't really have a way to deal with that because (1) they've already got Iran nearly maximally sanctioned, and (2) even if they could find something else to sanction Iran over there is no reason for Iran to believe that changing their behavior would lead to removal of that sanction.
No, by "sanctions" I do not mean any of those things. I mean the economic prohibitions against trade with Iran meant to dissuade them from continuing their nuclear program. The ones that Iran agreed to the Joint Comprehensive Plan of Action [1] negotiated between Iran and China, France, Germany, Russia, the UK, and the US in order to have lifted.
Anything that takes resources from Putin is worth it. China does not currently wage war in the center of Europe and neither it use terrorist attacks against civilian population in countries that compete with them.
That's because they do all of the above, and more, indirectly, using Russia as their puppet. They are too smart to do this openly. But you know, Putin would not start the war if he wasn't sure of China's support.
