It’d be worth comparing your opinion to data, so you aren’t stuck with an unverified opinion.

Regardless of how the US ranks in terms of brain drain, and how that rank is trending, it's clearly an area where the government wants to compete.

As of this year, the US employment-based green card backlog for citizens of India is such that they're currently still processing applications filed in 2019 for the top EB-1 category (that's "Extraordinary People, Outstanding Researchers and Professors, and Multinational Executives and Managers"), and 2012 for mere PhDs. So the numbers would have to go down a lot for US to even notice.

Speaking as an immigrant myself, so long as there's still noticeable wealth disparity, people will make the jump. The other aspect that makes US specifically especially attractive compared to some others is its family immigration policy - people generally want their family to join them eventually, and US has an unusually large allotment for that compared to many other countries.