Nothing Gold Can Stay was the reflection of the seasonal cycle of nature. The poem though a short one symbolizes what a Mother Nature cannot hold for long the 'Gold' but respects its value/worth.
Explanation:
In this poem, Robert Frost brings out the deep meaning of how few things that are of high value/worth are not treated properly/not respected for their worth. He talks about how Nature (In the poem, he keeps referring it as 'Her') being the Mother of all subjects on Earth.
He starts explaining about the season with a leaf, its color and how it slowly transforms into a bud, turns into a flower and then eventually, a fruit. This cycle, Frost writes in the most metaphorical way for readers to understand what we need to take an advantage of and what we must value, accordingly.
This poem is a classic example of how humans forget what is worthy as we can find it everywhere and look out for things that we do not have in our surroundings.