yes. reverse osmosis (a sort of filtering) is the most effective and efficient way on the large scale, but it is still not very efficient and it is expensive (requires a lot of energy) and you get a small proportion of pure water from a large volume of salty water so lots of water is needed to be treated to satisfy any large need for fresh water.
Which is one reason it isn't done a lot yet. Still generally cheaper to get water from very far away and pipe it than to produce it at the place of use from seawater. That is changing, of course, because there is a fixed amount of fresh water available and you can only go just so far away to satisfy a local need before it becomes absurdly difficult and expensive as well (and the people where they take the water are starting to say NO you can't have it)