The essence of a modern economy is to help one with lesser resources gain access to extra resources, which could be used to invest in areas that matter and be productive in order to stand out and meet up with innovation.
 
The problem starts with either loans coming with high interest rates, making it difficult to meet up the demand, or the most common issue is spending that borrowed money on things that can't be accounted for and having no plan of repayment being laid, which is why some governments go from loan to loan, servicing existing loans, and also borrowing new ones to hand over debt to upcoming ones instead of reducing it.