Sauté the Aromatics: In a large pot, heat olive oil over medium heat. Add the chopped onion, diced carrots, and celery. Sauté until fragrant and the vegetables are slightly soft, about 5-7 minutes. Stir in minced garlic and cook for an additional 1-2 minutes.
Add Cabbage and Tomatoes: Gradually stir in the chopped cabbage and cook for another 5 minutes until it begins to wilt. Add in the canned tomatoes with their juices.
Pour in the Broth: Carefully pour in the vegetable broth and season with thyme, salt, and pepper. Bring the mixture to a boil.
Simmer: Reduce the heat, cover, and let simmer for about 20-25 minutes or until the cabbage is tender.
Taste and Adjust: Taste the soup and adjust seasoning if necessary.
Garnish: Serve hot, garnished with fresh parsley if desired.