Preheat oven to 375°F. Lightly spray a 9x13 baking dish with nonstick spray.
Crush pretzels in a food processor or zip-top bag. (Not too much) In a large bowl, combine pretzels, brown sugar, flour, and vanilla. Stir in melted butter. Press mixture into the baking dish in an even layer, reserving ½ cup for topping.
Bake for 10 minutes. Cool completely.
In a small saucepan, combine blueberries, sugar, lemon juice, and cornstarch. Stir and cook over medium heat until the mixture thickens and the berries burst (about 5–7 minutes). Remove from heat and let cool.
In a medium bowl, beat cream cheese with an electric mixer until smooth (2–3 minutes). Add powdered sugar and beat until combined. Gently fold in Cool Whip until smooth and fluffy.
Once crust is cooled, spread the cream cheese mixture evenly over the crust. Spoon blueberry pie filling over the cream layer, then drizzle the cooled homemade blueberry topping over that. Sprinkle reserved pretzel mixture on top.
Cover with foil or plastic wrap and refrigerate for at least 4 hours or overnight. Slice, serve cold, and enjoy!