Magna Carta is hailed as such a human rights achievement but it isn't. It protected barons, not all people, to a fair trial. There were still peasants. Peasants had no real rights, only the nobility (barons) did. But hooray for Eurocentric history.
I understand your complaint, and truly, a part of why this is heralded
is eurocentrism, one must not forget that.
However, people knowingly limiting the power of a king is an achievement. Be it the mandate of heaven in the Chinese dynasty, or the chosen one of the Abrahamic god in numerous european nation-states, absolute power was rather, well, absolute. The ability to break that from the "grounded" side of the heaven-king-people relationship was a feat.
Now, in truth, did the main part of the magna carta have any immediate effects for the peasantry? Perhaps not. But that initial stance against the king would allow for further opportunities by them down the line.
It's why I don't take offense to England appreciating a piece of history. If I were to reflect on the Declaration of Independence, one might have a valid objection to the phrase "all men are created equal" versus the reality of the day (and today). But it is the ramifications of it (In places such as France, Haiti, the U.S. itself, et cetera) that makes it celebrated.