Preheat oven to 425°F.
In a large skillet over medium-high heat, cook the beef and onion. Break the meat apart with a wooden spoon and cook until the fat has rendered and the meat is browned (8-10 minutes). Stir in the taco seasoning and ½ cup of enchilada sauce. Reduce the heat and let simmer for 5 minutes. Stir in the cream cheese until melted (1-2 minutes), then remove from heat.
Warm the tortillas in batches in the microwave in 30-second intervals until pliable. Brush one side of each tortilla with olive oil, flip them over, and spoon 2 tablespoons of the beef mixture onto the unoiled side. Roll up tightly and place seam-side down on a baking sheet. Repeat with remaining tortillas.
Bake the taquitos until they begin to crisp (about 10 minutes), then flip and cook until fully crispy (4-5 more minutes). Remove from oven, keeping the temperature at 425°F.
Coat the bottom of a 9×13-inch baking dish with 1 cup of enchilada sauce. Arrange the taquitos over the sauce, then top with remaining sauce and shredded cheese. Bake until the cheese is melted and bubbling (8-10 minutes).
In a medium bowl, mix the chopped avocados, jalapeño, cilantro, lime juice, and a pinch of flaky sea salt.
Top the taquitos with the avocado mixture and sour cream. Serve warm with lime wedges for squeezing.