Majority of altcoins are centralized and have no new ideas, they just rehash the same old ideas over and over with a new name and new advertisements. This is why they don't have real potential and any "opportunity" is just short term profit making at a very high risk.
It looks like new Alt coins are launched with aim of just grabbing investors money. Now we have hundreds of thousands of alts in the market and it's natural that worth of alts has to go down due to so many alts circulating in the market. Moreover Alts are launched with claim of novelty and innovation but majority of them failed to deliver that or are either abandon by founders soon after the fund raising phase is completed.