Nobody says that deflationary currencies cannot work as a medium of exchange.
...In reality, most people are reluctant to use deflationary assets for daily spendings.
You will have a difficult time supporting that statement. In fact, gold is fairly deflationary, and yet it has been used as money for centuries.
The claim that people won't spend deflationary money is an exaggeration. Clearly, if the money is deflationary, then people may spend less, especially on unproductive assets or on things that have little value, but that is actually a benefit.