In the more than 4 billion years since the emergence of organisms, the earth's environment has been constantly changing, sometimes extremely hot, sometimes cold, the sea has turned into mountains, and humidity has replaced drought. Under the pressure of severe natural selection, most species were unable to adapt to this change and were eliminated. Only a small number of species whose body structures became complex in evolution, became more adaptable to the environment, and gradually evolved into new groups, they can use environmental resources more effectively and leave more descendants. In fact, in the long years from ancient times to the present, the formation and extinction of species have never stopped, but low-level organisms will not completely disappear, nor will they all evolve to more complex levels. So in today's world, there are both low-level single-celled algae and complex angiosperms.
However, it must be noted that evolution is one-way and irreversible, and it is impossible for evolved species to return to their ancestral form. Once an organ evolves, it will not return to its original shape in its descendants, nor will it reappear in its descendants.
Although modern ferns belong to the same group as ferns hundreds of millions of years ago, their organs and structures have changed, and the current natural conditions are not what they were when seed plants first appeared, so modern ferns cannot evolve into seed plants.