I bet you've not seen a mustard seed, but you still get what is being said, in the parable of the mustard seed.

If the parable is talking to a foundational reality, rather than cultural situations, I think it can endure.

I get what you are saying, but even parables don't have 'the truth'. I would imagine that there may even be parables that argue the opposite position. And both, opposing positions could be right, depending on the context.