If a few people hold most of coins without using them then we won't see it's full potential. It's takes the proper use of money to make money.
This is pure Keynesian brainwashing bullshit-theory. Almost 100 years of bullshit hammered into the minds of billions of people will take some time to get out of their heads again, thats for sure. But bitcoin and other cryptocurrencies will hopefully within the next 20 years manage to kill this myth once and for all.
R.I.P Keynesian economy. You have ruined enough lives now. Time to go sleep 6 feet under.