I disclaim that I am not a well read person in the case of Hindu scriptures. So I would be glad to be corrected by more knowledgeable people. Having said that, I would like to make a point by point rebuttal:
1. It's indeed true that a child does not have any gunas and needs+ https://twitter.com/vaish_mufc/status/1324684340828295168

+to develop them over some time in his/her early life. However that doesn't mean a child is born without varna. The correct interpretation is, that a child needs to develop appropriate gunas as per his/her varna, and not otherwise.
2. It's highly stupid of us to believe the+

+claim of the British regarding the caste system that it was made rigid by Hindus (~10%) and the rest of it was done by the British. That's highly ridiculous. The jaatis that exist today have always existed, much much before the British even came to India. So to say that they +

+were made "rigid" by the British and there was no such concept before that is incorrect. Every jaati has its own history of existence ranging from thousands of years to merely a few centuries differing from jaati to jaati. So ma'am these were not made rigid by the British, but +

+they have always been rigid. Also varna based on gunas and professions was a reality but only in the cases where entire jaatis took over the occupations as well as had the qualities to be inducted into another varna. Only in such cases varna of jaatis, and NOT individuals was+

+changed. This was rare however. And even if it happened, it was true for jaatis as a whole, and not individuals, and I repeat this point coz this is the crux. So there wasn't a British intervention but this system existed thousands of years before they came. Thank you

https://twitter.com/IndicSeeker2020/status/1309812147765960711?s=19 one may also refer to my pinned thread related to jaati and varna if interested. It specifically talks about the tradition/ritual/deity specific aspects of jaati and varna.