I think Main problem of crypto is adoption but eventually no matter how hard we do think off we cant really go to a point that we can able to go on full scale.
We need to find a reason of why the adoption of bitcoin or crypto is less or not as much as it should be. The reason for this is that bitcoin price is not stable and it is too much volatile. When the price is so much volatile, no buyer will be willing to accept it as a payment method, as they never know if its value become less in matter of hours.