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.
I totally agree with you that when making an investment, we have to go for altcoins that really have working products, this is what I do, and this is why I found it very difficult to participate in Pre-ICO, because I feel there is no way you can know if a project really have use case except they have been tested and confirmed, and the only way they can be tested and confirmed is when they have already entered an exchange, and overtime, you have seen the seriousness of the team, and able to monitor if they are really working according to the purpose for which they were established, and also working in line with what is being documented on their whitepaper, if they are following upon their whitepaper promises, then they are worthy to be called an investment.