Houti aggression on merchant ships is a political act. By attacking Israel they are sending a political message to their opponents that reads "if you attack us right now it means you're on the side of Israel". That's why it doesn't matter whether their garage built cruise missiles actually make it to Eliat, or not, whether they really stop shipping, or not. The shots are fired north at Israel, but the message is targeted south and east. They are in the middle of a civil war, a very long and extremely brutal one, and this tactic works given what their opponents think about themselves and the world.
The EU/US response to this will be challenging, mostly because they cannot really threaten Houti power. North Yemen is already in a deeper ruin than most countries are after a war, their military industrial base is located in another country (Iran), and there are very small chances for an internal revolt. BTW, in this conflict China and the US and the EU are actually on the same side, though China will definitely try to sit this one out.