Belonging to an established older form taken as a standard. Classical is a claim about lineage, not about quality.
From classic, Latin classicus (of the highest class), from classis (a class, a rank) — the same root as 'class.'
Calling a thing classical says where it sits in a sequence, never how good it is — a classical form can be surpassed by a newer one and remain classical regardless, because the word answers a question of descent and precedence, not one of merit.