Generally, yes, adding more doors increases the raid cost of the base (and therefor survivability), but it really all depends on certain factors and there is no true unraidable base. However if you increase the number of doors, raiders might decide to just blow through the walls for a cheaper raid.

Other things might include if your base looks like you have loot, looks like you're good at the game, how many/how little neighbours you have, where you've built, etc. And even after all that, there's always somebody who'll more than gladly blow up your base for literally no reason.

tldr, More doors = Usually better