Heat oil in a large soup pot over low heat. Add onion and cook until soft and translucent, about 5 minutes. Stir in celery and cook for 5 minutes. Add carrots and cook for 5 minutes. Mix in garlic and cook until white, about 2 minutes. Add diced tomatoes and cook until heated through, about 3 minutes.
Season soup with basil, oregano, and pepper. Add water and vegetable soup base and bring to a boil, about 5 minutes. Reduce heat to a simmer and cook until vegetables are tender, about 5 minutes more.
Add zucchini and summer squash to the soup and cook until tender, 3 to 5 minutes. Stir in eggplant and cook until tender, about 5 minutes more. Fold in cooked pasta and adjust seasonings.