Given slavery was not abolished at the time of independence, it seems likely that the writers of the constitution did in fact not intend to apply rights to all humans as broadly as possible.

What it means now? Who knows.

That's in the Declaration of Independence not the Constitution. The former is high prose. The latter is a legal document. As a legal document, it cannot purport to give rights to people outside of its jurisdiction.

The Constitution does not purport to give rights to anybody. It declares that certain things are rights and prohibits the US government from violating them.

You're confusing the declaration of independence, a fluff document, with the Constitution, a legal document. Fluffy language aside, in the Anglo-American tradition, rights derive from legal documents (or precedents), and the right to habeas corpus or a jury trial derives from the Constitution and is circumscribed the the territorial jurisdiction of the Constitution.

This is all well and good, yet doesn't matter if the majority have no interest in seeing them enforced.