How do you know then which of the altcoins has real potential and that's why investing in altcoins is very risky because we don't know which one will make it. Not all altcoins rise with Bitcoin when it rises, some also falls as traders dump them to buy Bitcoin. If you're unfortunate and buys those that'll be getting dumped like the memecoins, you'll lose. We don't have to limit our investment but when investing in altcoins we have to be extra cautious.
It's better you avoid investing in altcoins totally because they can make you to lose money more than making you money, altcoins rise fast and give huge returns than Bitcoin but they also dump faster because many of the altcoins are just used for pump and dumps by whales.
Therefore, altcoins can be used for trading, perhaps even short-term and sometimes medium-term, for long-term investments, I would not buy altcoins, as it seems to me too risky. But for short term trading altcoins seem to be not a bad option, I follow a few of them and see that there are those who are more volatile than others, this seems like a good chance for me to trade, but I am a long term investor, I buy bitcoin and do not trade yet, I just watch and study trading when I have time for it.