Sanctions are a wasting asset: the shadow fleets, alternative payment rails and re-invoicing hubs built to evade one regime remain available to the next target. Each round of restrictions subsidises the workaround economy that blunts the following round.
Design for decay
That does not make sanctions useless; it makes them time-limited. Regimes designed with explicit objectives and sunset logic extract their coercive value early, before the plumbing routes around them.