In a large saucepan, add the berries, sugar, cornstarch, and lemon juice. Cook over medium heat. Cook for 5-7 minutes or until mixture has thickened trying to stir without breaking up the berries. Remove from heat and stir in the vanilla and salt. Let mixture cool for at least 15 minutes.
Preheat oven to 375℉ and roll out the pie crust into a 12-inch disc on a floured surface. Place it on the pie pan and crimp the edges.
Pour the filling into the pie crust. It can still be warm.
For the topping: Combine the flour, sugars, butter, cinnamon, and salt using a pastry cutter or a food processor. Crumble on top of the berry filling. I like to kind of squeeze it into chunks for more texture. It seems like a lot of topping but it melts down.
Bake for 60-70 minutes. Check at 45 minutes to see if the top is browning too fast and cover with foil if needed. Let pie cool completely (this will take a few hours). Serve warm or at room temperature with ice cream.