I know the question sounds weird, so I'll bring an example coming from my field: mathematics.
One of the greatest mathematicians of all time is Gauss. One of his results is the "Remarkable theorem" in differential geometry, whom he proved in 1827. Even if it was a truly remarkable achievement, today, a good undergraduate student would be able to understand well* its statement, and the path to it. So we could say that Gauss's discourse is "easier" to understand today.
It seems like something like this happens in philosophy. As a first impression, one might say "no", and this is because, from my experience, no one used to understand Hegel in high school (yep, down here in Italy we study it). But maybe it just works like maths: you'll have to understand what previous mathematicians said in order to understand the next ones. And we basically lost track of it since Plato, back in school.
When Kant first released his arguments, it seems likely that it would have been confusing for even the best philosophers, but now, an undergraduate can read the Critique of Pure Reason and understand it well. It seems like such a phenomenon might be an answer to the question "Why is older philosophy 'easier' to understand?"
(*) This does not mean everyone will eventually well understand it: just sufficiently talented students.