Altcoins with real use case will never disappoint you on the long run ,altcoins like clear foundation ,Hot (hologen) and skycoin will never disappoint because they have a real use case ,if you choose wisely you Wont have anything to worry about.
There are some altcoins that are BIG if you know how to pick them out ,some are backed by popular bigger companies like Microsoft among others.
Do not choose coins because they are mineable or they have implemented POS ,without real use case they will die overtime and lose value.
Yes you're right. choosing coins that use POS consensus without real use, it can't be expected. so don't buy this coin.
but that doesn't mean POS is bad. POS is also good if the project is already working.