"Modern legal systems generally recognize people's present legal status..."

Example:

Suppose someone's great-great-grandparents were citizens of Country A.

The person today is a citizen of Country B.

Modern legal systems usually determine that person's rights by their current citizenship and legal status, not solely by distant ancestry.

Similarly:

Suppose someone's ancestors owned land centuries ago.

Modern courts typically require present legal title, applicable statutes, and current property law rather than relying only on ancestral ownership.

This does not mean ancestry is never relevant. Some legal systems recognize ancestral claims in specific contexts. The point is that modern legal systems generally require a legal basis in addition to historical ancestry.