yes it is the effect. It is the effect of saying something true

So when we look around to see the art we have, this is something that sticks out about the timeless ones

No I don't think anything "good" *requires* an art defining or describing a period of time. More often good things transcend the period of time they were created in. To the extent that they do reflect a period of time it's because other, lesser artists followed their lead, over-saturating the art with a particular style for a period of time.

A great artist may define or describe a period of time incidentally, but you can be good without inspiring copycats, even if copycats are generally a sign of something being good.

tldr The cause of being good isn't that it defined/described a time. That's the effect if anything.

k00b

Stacker Saloon

saloon

I wonder if you agree with this:

If a band’s body of work should be qualified as “good”, then it should define/describe the period of time it belongs to, as one of its requirements 