When a fan asked Magic head designer Mark Rosewater about how Mangara's ability contradicts what Rosewater thought about white's "intentional downside", here's what he said on his Blogatog:
Many MTG fans have criticized white as being the most underpowered color in Magic due its lack of cards that could draw cards, so it makes sense that R&D are giving white more card draw power to help balance Magic's color pie.
Magic designer Ari Nieh, a.k.a. the "White Council of Colors representiative", recently confirmed that Mangara's reactive draw ability is not the only white card draw experiment you will see in the next few years.
When we looked at white card draw, we decided that any white card with "Your opponents can't do X" also allows the text "Whenever an opponent does X, draw a card".— Ari Nieh (@SixthComma) June 4, 2020
This is not the only white card draw experiment you'll see over the next few years.#WotCStaff https://t.co/CC5XEeOxC8
Core Set 2021