That is the same as when a Brazilian would like to visit the US. This general waiving of requirements simply guarantees that Brazil's the only one getting the short end of the stick. A negotiated reciprocal agreement would be much better.
It would also be completely unrealistic as millions of Brazilians would just go to the US and stay there. Reciprocity doesn't work between countries with significantly different wealth and standard of living.
I've been on the receiving end of US visa process. They require you to demonstrate that you have substantial ties to your country that would make it more likely that you'll eventually leave the US. Income, real estate or other assets, children/wife staying, that kind of thing. That's not a guarantee you'll return, of course, it just makes it more likely.
Millions? I don't think so. Maybe a few thousands? I think you overestimate the amount of people in Brazil who fancy a life in the US. Furthermore, I also think you overestimate the amount of people who, fancying a life in the US, are actually able to secure financial and social resources to move there.
Brazilians have visa-free access to Europe[0] and you don't see "millions of Brazilians" just going there and staying. Why would it be different?
[0] Technically there's a visa which is granted on arrival
Sometimes, Brazilians in US are categorized as Latinos but in reality, outside Boston and maybe Florida, there isn’t that expressive Brazilian communities in the USA.
Protip: Go to Carioca in Astoria or Copacabana on 39th Ave. Holy shit Brazilians can cook.
I have found their immigration process so onerous, I decided against it. One of the most irritating things was, my wife would not be able to work for 5 years (IIRC, it's been a while) if there are _any_ Germans whatsoever willing to take the job she'd be applying for. She's an accountant, so that would definitely be the case. I mean, I see the point of all this _for Germany_, but that definitely put them at a disadvantage in attracting me to work there, in addition to much lower pay that my profession gets in Germany (which, ironically made the second income much more desirable).
People in the US seem to think that EU is this open borders paradise where "ihre papiere bitte" is not a thing. It very much is a thing.