Heat olive oil in a large pot over medium heat. Add diced onion and sauté until translucent, about 5 minutes. Add minced garlic, diced carrots, and celery; cook for another 3-4 minutes until vegetables begin to soften. Stir in rinsed lentils, diced potatoes, diced tomatoes with juices, and vegetable broth. Add ground cumin, smoked paprika, dried thyme, dried rosemary, salt, and black pepper. Bring soup to a boil, then reduce heat and simmer uncovered for about 35-40 minutes, or until lentils and potatoes are tender. If using spinach or kale, stir it in during the last 5 minutes of cooking until wilted. Taste and adjust seasoning as needed. Serve hot, garnished with fresh parsley.