Ligand exchange reactions... are they one way or reversible?
Let's take the binding of $\ce{O2}$ and $\ce{CO}$ to hemoglobin as example. $\ce{CO}$ does bind much better than $\ce{O2}$!

We can consider the reaction of oxygen-loaded hemoglobin with $\ce{CO}$ a ligand exchange reaction. If that would be completely irreversible, the logical consequences in the case of an intoxication would be: [...] six feet under ;)

Instead, intoxicated patients are treated with oxygen at higher pressure.

To me, that sounds like Le Chatelier in the ICU and it only makes sense in the case of equilibria.