Is it a problem, say, if we all achieved nirvana but some achieved better nirvana? Must we rebel against them too?
> Calling the modern middle-class human a peasant is quite misguided imo.
The modern middle class is shrinking fast. About 17%. Most people are either low income or poor.
> It is important to acknowledge that we have fared much better than our ancestors.
Look, we generally live much longer these days, so I think that's a decent measurement that we're far better off in aggregate compared to the middle ages. However life expectancy has actually been decreasing recently in many places, and we have some really big global problems to solve if we don't want that trend to continue. If that trend does continue though, then it becomes very hard to say we're better off than our ancestors.
> Is it a problem, say, if we all achieved nirvana but some achieved better nirvana? Must we rebel against them too?
Probably yes. Most people aren't zen. It's in our nature to measure our status among our peers, and probably responsible for most people's wealth and their drive to do better. Better is always relative. Before arguing the morality of this, you'll need to also defend the morality of billionaires (what's the point really?).
I think this depends on how you classify peasant. If we can agree that it's about income inequality, and not quality of life, then there was a study done comparing income inequality in the late eighteenth century to current day, which concluded that "Incomes were much more equally distributed in colonial America than in America today, or in other countries in the late eighteenth century". https://www.nber.org/papers/w18396
Ultimately it depends on the specifics and the dates we are comparing. I don't think people fully realize how significant income inequality really is today.