Hey all as corn flour is not that good for our health so for alternative you can also use rice flour. I have tried to make this soup using rice flour and it was amazing.
You can replace cornstarch with grind boiled potatoes it's thicken the soup and taste much better. I personally don't like the taste of cornstarch so that's the best way to enhance the flavour of soup .
Instead of cornflour try adding mung daal, coock it without haldi and cook for 5-6 whistles or it's all mushy, it affects the taste a bit but tbh it's far better than cornflour
I would advise you to use vegetable stock insted of normal water Vegetable stock : Take little more than optimal water for soup and add in a pan.....now add few cabbage leaves, leftover vegetable peels, Some spinach and some beans and boil it till its gets the aroma of veggies and little bit turns translucent. now use this stock instead of regular water in soup.