Part of it too is not just age but also careful engineering to breed out bitter compounds. Case example: brusselsprouts

"About 30 years ago, a Dutch scientist identified the chemicals that made brussels sprouts bitter. He selected seed varieties with lower levels of the bitter chemicals and bred new high-yielding varieties that tasted less bitter."

source: https://www.iowafarmbureau.com/Article/Its-not-your-imaginat...

some of it is to do with age too though. :P