You're comparing what the Framers of the U.S. Constitution (who were busy trying to form a new government) did over 230 years ago to today? That's an apples and oranges observation.
Women didn't even have the right to vote at that time. They since obtained the right to vote in 1920. Slavery and indentured servitude was an acceptable practice at that time, though it was highly controversial even then. Slavery was eradicated in 1865, with many other civil rights issues addressed as the U.S. matured. Jim Crow laws were enacted in certain parts of the U.S. in the late 19th and early 20th centuries, which meant a huge step backwards, but the last of those laws were eradicated in 1965.
Slavery was such a hot button issue when the Framers began forming the Constitution that they deliberately put it aside. Several reasons for that, in addition to the more pressing and immediate issue of getting a Constitution ratified. Concerns over private property rights and protection of same overruled the need to immediately address slavery. Franklin, in particular, believed that emancipation would eventually come about.
No country is perfect, even Canada, but the Framers ensured that they created a system whereby inequities could be addressed within that framework.
One item of interest, perhaps: The Framers had a completely different outlook toward women than most Americans today.
This article from the Smithsonian addresses some of that and, in particular, with how some Framers interacted with women who were not their wives.
The term "Coverture"
as adopted from English common law, restricted women, particularly married women, who required them to adopt their legal status from their husbands. It didn't take long for women to begin activism toward suffrage.
Federalist 54, as written by James Madison under the pseudonym Publius addressed slavery only within how seats in the House of Representatives were to be apportioned. Madison recognized slaves as both being property and people and thus proposed a solution, the so-called "three-fifths" solution which allocated a single slave as three-fifths of a person. This was eventually annulled by the 14th Amendment.
My point in all this is that the Framers were aware of these issues (blacks and women) but could not address those at the time. It took time and even some blood to get to where we are today.