That massive underclass existed long before capitalism. Agrarian societies have had poor people going back longer than recorded history, they also generally had slaves and or some form of serfdom.
Humans also caused massive environmental devastation going back to the Stone Age and across all economic systems. In the Americas only 1 in 6 mega fauna species alive 50k years ago survived to 10k years ago. In Australia it was 1 in 8.
Things have gotten worse but that’s less that individual humans have become more destructive, it’s mostly the simple fact there are more humans.
In theory a better option could exist we haven’t actually implemented anything better, humanity has tried many systems not just feudalism, communism, and capitalism and it’s the clear winner by the overwhelming majority of metrics. Mercantilism, tribalism, etc all have some upsides for some segment of the population but don’t result in nearly the same levels of widespread prosperity.
What we consider extreme poverty was normal throughout most of the globe and most of human history.
At least initially feudalism was economically worse than the the Roman imperial system in terms of output per person. It’s stable politically, but not objectively better.
Output increased overtime as technique and technology continued to improve, but that’s not a function of the feudalism specifically.
Humans also caused massive environmental devastation going back to the Stone Age and across all economic systems. In the Americas only 1 in 6 mega fauna species alive 50k years ago survived to 10k years ago. In Australia it was 1 in 8.
Things have gotten worse but that’s less that individual humans have become more destructive, it’s mostly the simple fact there are more humans.