Why is hashing not safe?

Why is hashing, which is often seen as a fundamental aspect of ensuring security in cryptocurrency transactions, not considered completely safe? Are there inherent weaknesses in the hashing algorithms used, such as the potential for collisions or the ease of brute-force attacks? Additionally, how do other factors, like the increasing power of computational hardware, affect the security of hashing-based systems? Could the evolution of quantum computing pose a significant threat to the security of hashing in the future? Understanding these concerns is crucial for anyone interested in the security of cryptocurrency and blockchain technology.