If someone buys a coin in the spot market, they got nothing to worry about since even if the price drops significantly, they will still have their coins in their wallet and they have the option to keep them until the price recovers back and gets higher than the point of buying so that they can sell.
This strategy is for bitcoin. It doesn't work with most altcoins, even those in the top 10. If you bought Ripple at $3 in 2018, how long do you think you have to wait before your investment returns to cost? It's been over 5 years now, but XRP is still far from that value and it's not certain it will reach those values anytime soon. So the notion that altcoins on the spot market can be held indefinitely until they return to their price values is actually a huge misconception. The only thing you can do in altcoins all the time is sit at a loss, or with those coins that have turned into a mountain of junk and no one else wants them.
Yeah, perhaps. Altcoins are always too risky to be held for long-term, no matter how famous or trusted they are at the moment of buying, you can never really know if you are ever going to get even an ROI after investing in an altcoin. As you said, even some of the coins that used to be in the top 10 are now struggling to reach a good price point.
Those who are to invest in altcoins should always check their history and how they have been doing for the past couple of years at least, if a token is new, it's better to avoid it, but if it's old, a bit of research before the investment should do well.