Holding is not very dangerous. Each investment carries some risk. It depends on what coins you keep. If you have good and promising coins, it's definitely worth holding. Before investing you need to do research to avoid buying shitcoins.
Holding altcoins is dangerous but holding fiat euro, usd or holding gold and silver is dangerous too. There is nothing risk free in this world. Holding alts is the only way to make money as you integrate into the system.