What would happen if every species evolved to be perfect?

Answer 1

In the simplest possible terms: there's no such thing.

Evolution drives populations to adapt to changing circumstances. Even if you have a species that's more or less ideally adapted to the environment it lives in, there's no telling when that environment might change, making the current state less than ideal.

Also, evolution doesn't "strive" to achieve perfection. Evolution is about what organisms manage to produce just barely more offspring than the others. If a less "perfect" organism somehow manages to out-breed the rest, that'll still be the more common type in the next generations.

Answer 2

If every species evolved to be perfect, there would likely be little to no competition for resources, resulting in overpopulation and potential environmental imbalances. Evolution relies on diversity and adaptation to changing environments, so a lack of imperfection could hinder the ability of species to evolve and survive in the long run.