Too broad a brush. It shows how there are those who don’t believe in spite of seeing how many were healed. No one can reach that mindset, so they live in their misery.
There are many many who believe today but too many have unbelief. They know/believe God heals but ‘will he do it for me’ mindset.
Mark 9:23 “’If you can’?” said Jesus. “Everything is possible for him who believes.”
Mark 9:24 “Immediately the boy’s father exclaimed, “I do believe; help me overcome my unbelief!”
An excellent point!