Modern missile boats are strongest in coastal defence

How useful are missile boats in the modern Chinese or Russian style?

They are excellent for a defensive war near the coast, where numerous small launch platforms can add a difficult layer to a wider anti-access defence.

Missile boats are an effective defensive tool rather than a universal naval solution. China gains particular value from deploying many of them around the South China Sea, where they add mobile launchers to a layered coastal defence. Shore-based missiles are powerful but can be located and attacked, while a ballistic weapon such as the DF-21 also creates escalation risks because an opponent cannot know its warhead or target immediately after launch. Numerous small boats complicate surveillance and targeting in a different way, making them a more persistent practical threat once geography and concealment favour the defender.