[misnome]

> nature is incredibly smart

No, nature is not smart. If some feature helps you survive - even if it would be 'judged' bad in some other context - it is being selected for. That's evolution

> a modern bulldog's health is frail compared to its ancestors, hardly what one would call evolution.

And yet here it is, survived. The difference between selective breeding and evolution is just nuance and speed really, from the fact that it has some intelligent being with 'purpose' selecting deliberately.