I'm wondering whenever it's worth buying and holding old coins for the long term. Primecoin is one of its kind with a PoW algorithm that contributes towards the discovery of prime numbers. It's a pity other crypto projects haven't copied its model.
There are some good old coins out there with real life utility like PundiX however as new projects are emerging, it is wise to learn from these older ones. I believe that these older ones are quite secure and much richer qualities compare to newer ones. However, newer ones like DeFi projects are hot due to its use cases and to generate passive income. Unless these old coins adopt and make positive improvements, they'll stay left behind.