As stated in JOSH's answer, a "unicorn" in this context is a start-up company that is valued at $1 billion or more.
Every investor is chasing something shiny, they do not care for the ecosystem at all.
The author is saying that investors are so focused on chasing unicorns, that they neglect their "ecosystem", or other start-ups.
In the world of unicorns it is really hard to see any other animal.
In other words, investors typically only invest in start-ups that they believe will become unicorns, which prevents start-ups that don't look as promising from receiving enough investments to prosper.
In a world where everyone is looking for the next billion dollar opportunity, other opportunities get neglected.