You're looking purely at the theoretical possibilities of crypto while ignoring the reality of a situation in which major sanctions are enacted. Who are the people who are going to be selling their services to Russia in a situation like this? You can already see companies that haven't chosen to suspend business in Russia (even though there are no sanctions forcing them to stop) suffering major reputational damage.
Just because you could theoretically get around sanctions doesn't mean that any serious number of people would do it. It also doesn't mean that you can't get caught - it's not like you can untraceably provide services, so there's very much a nonzero chance you get caught.