It can be solved programming the right amount of zombies in the right places. But it takes time, effort, and you have to be creative and think.
Even with slow and stupid zombies, you can't avoid all encounters. Zomboid and the walking dead game are good examples of it.
A good game does not need to add artificial danger. Take any good hunting game. They do not add flying elephants. Why? It would be easy to add danger and difficulty that way, but it will just hurt the game.
The same way, adding running zombies hurts the game. It turns it into a shooter instead of a survival. It forces you to deal with them in only one way. You can't hide, or run, all you can do is kill them. And with the fact they are fast, you can't use melee anymore. It has to be guns. And the noise attracts more zombies. That you have to keep shooting to.
What are you saying? In those games your noise does not attract them? That makes it even worse.