Obviously altcoins have potential. If an investor want to invest for long term than check the fundamentals, members, roadmap, community and use case of it. For making short term and intraday profit, altcoins actually have potentials. Altcoins on centralized exchange are bit safe then decentralized exchange.
All that can be excellent and yet the project still fails, with altcoins it's only hype that plays a part in the high returns the project gives. When project get hype by influencer and big money spenders then the small investors jump on the trend in buying the coin and in return the project gets the publicity it wasn't getting previously and pumps. Many altcoins has given people lots of profit so the saying that investing in altcoin isn't profitable is a lie. Just that we should be careful of our investment because in as much as altcoins has given people lots of money, it has also made many people go broke.
With altcoins, you shouldn't always think long term. Hold the coins but sell whenever there's a confirmation of the projects not doing so well. Don't be a believer as the CEOs are all liers and will say anything to keep the reputation of their projects intact meanwhile the project is dead.