I want to understand more about this assumption. Just two things I'm asking for clarity on.

(This topic is relatable to Invisible hand, free lunch, free markets and efficiency)

ASSUMPTION ONE:No market power. No individual buyer or seller, nor any group of buyers or sellers, has the power to affect the market-wide level of prices, wages, or profits.

REALITY ONE:Our economy is dotted with centers of market power, from large corporations

to unions. Furthermore, employers have an edge in bargaining with workers because of the threat of unemployment.

1. How is the assumption the possibility of "market failure" or less than, optimal economic results? If possible, what are examples of real-life example?
2. Is it a reasonable market assumption in reality?