What almost always happens in the context of evolution is that things are tried out and what works sticks around until something changes and the species goes ex

What almost always happens in the context of evolution is that things are tried out and what works sticks around until something changes and the species goes extinct. Nearly every species that ever existed is already extinct. It's hard to predict exactly what will happen in the long term with evolution, but that doesn't mean "the species that are now populous will always remain so" is a good bet.