When I knew about cryptocurrency I went for research and I discovered Bitcoin and other coins in the market, I went to study the history of Bitcoin and it's growth and I saw how well it was, so I said to my self if Bitcoin can grow this big then I needed to fine a rising coin that has not grown too big and invest my money on it, thinking it will grow as Bitcoin did, this happened 6 years ago.
Honestly,there are some set of people regretting now not investing in Bitcoin but in altcoins. I think many of these people take this decision because they did any research on bitcoin and other coins. However, for those who did thorough research about Bitcoin and still ended up investing in alternative coins, I would say it is the eagerness to make quick gains in the cryptocurrency industry that led them to take that wrong decision.as for you op you should have also researched the other coins and compared them to see the best among them.
It is not really advisable to invest in altcoins, but the truth is that there are some altcoins that are not bad if invested after proper research. If someone does their research well, they can pick out some of the good alternatives coins. One piece of advice I would give to anyone who wants to invest in any alternative coin is to use only a small amount money he want to invest in cryptocurrency and invest the rest in Bitcoin.