Heat a large pot or dutch oven over medium heat and add the oil. Once the oil is hot, add the onion, bell pepper, and celery with a sprinkle of salt. Cook, stirring frequently, until the onions are translucent and the veggies are starting to brown, 7-10 min. If things are sticking to the pan, feel free to add a splash of water.
Add the garlic, chili powder, paprika, oregano, garlic powder, onion powder, thyme, cayenne (if using), salt, pepper, and sausage with a splash of water to scrape up the brown bits. Stir until everything is evenly coated in the spices. Cook until the sausage is nearly done, 5-7 min.
Add the tomatoes (including their juices), broth, and pasta. Increase the heat until the mixture comes to a low boil. Stir well, cover and cook on a low simmer for 10 minutes. Stir occasionally and monitor the water level--if the liquid seems to be evaporating really quickly, turn your heat down a little and add water as needed. If there is excess liquid when the pasta is getting close to being done, let it cook some with the lid off.
When the pasta is done, reduce the heat and add the milk and cream cheese and stir until the cream cheese is fully melted and incorporated. Add the parmesan cheese gradually, if using, and stir until melted. The sauce will thicken as it cools so don't be alarmed if there is extra liquid!
Assemble. Divide the pasta between three meal prep containers and allow to cool completely before putting it away. Garnish with parsley (if desired). That's it!