"Written long ago". You say that like it means that it's irrelevant. As if, well, back then, they meant such and such but screw that -- today it means "Americans".
Yeah, it was written long ago. That's where we have to go, however, to find out what the Founding Fathers meant. And when they said "the people" they meant "the people at large".
And the people at large excluded non-whites, women, children, and non-citizens.
It no longer excludes non-whites, 15th amendment, or women (19th amendment), or the poor (24th amendment). It still excludes non-citizens, although the Supreme Court has ruled that in some cases even non-citizens are included. But since you were basing that on who was allowed to vote in federal elections, I guess we can say it still excludes non-citizens.