Brown the beef. In a large skillet or Dutch oven, cook the ground beef over medium-high heat until it is browned and crumbled. Drain off any excess fat.
Add aromatics. Add the diced onion to the skillet and cook for 3-4 minutes until it softens. Stir in the minced garlic and cook for one more minute until it smells fragrant.
Season the meat. Sprinkle the taco seasoning and ranch dressing mix over the beef.
Stir everything together so the seasoning coats the meat evenly.
Add liquids and pasta. Pour in the beef broth, water, and milk. Scrape the bottom of the skillet to loosen any browned bits. Add the dried pasta and stir well.
Simmer. Bring the mixture to a boil, then reduce the heat to low.
Cover the skillet and let it simmer for 12-15 minutes. Stir it once or twice so the pasta does not stick.
Add the cream cheese. Once the pasta is tender and most of the liquid is absorbed, add the cubed cream cheese. Stir until the cream cheese melts completely and the sauce becomes creamy.
Finish with cheese. Sprinkle the shredded cheddar over the top.
Cover the skillet again and remove it from the heat. Let it sit for 2-3 minutes so the cheese melts.
Serve. Stir the melted cheese into the pasta. Taste and add salt and pepper if needed.
Serve hot with your favorite toppings.